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4<head>
5 <title>LLVM Programmer's Manual</title>
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9
10<div class="doc_title">
11 LLVM Programmer's Manual
12</div>
13
Chris Lattner9355b472002-09-06 02:50:58 +000014<ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +000015 <li><a href="#introduction">Introduction</a></li>
Chris Lattner9355b472002-09-06 02:50:58 +000016 <li><a href="#general">General Information</a>
Chris Lattner261efe92003-11-25 01:02:51 +000017 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +000018 <li><a href="#stl">The C++ Standard Template Library</a></li>
19<!--
20 <li>The <tt>-time-passes</tt> option</li>
21 <li>How to use the LLVM Makefile system</li>
22 <li>How to write a regression test</li>
Chris Lattner61db4652004-12-08 19:05:44 +000023
Reid Spencerfe8f4ff2004-11-01 09:02:53 +000024-->
Chris Lattner84b7f8d2003-08-01 22:20:59 +000025 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +000026 </li>
27 <li><a href="#apis">Important and useful LLVM APIs</a>
28 <ul>
29 <li><a href="#isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt>
30and <tt>dyn_cast&lt;&gt;</tt> templates</a> </li>
31 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro &amp; <tt>-debug</tt>
32option</a>
33 <ul>
34 <li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
35and the <tt>-debug-only</tt> option</a> </li>
36 </ul>
37 </li>
38 <li><a href="#Statistic">The <tt>Statistic</tt> template &amp; <tt>-stats</tt>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +000039option</a></li>
40<!--
41 <li>The <tt>InstVisitor</tt> template
42 <li>The general graph API
43-->
Chris Lattner261efe92003-11-25 01:02:51 +000044 </ul>
45 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +000046 <li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +000047 <ul>
Chris Lattner261efe92003-11-25 01:02:51 +000048 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
49 <ul>
50 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
51in a <tt>Function</tt></a> </li>
52 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
53in a <tt>BasicBlock</tt></a> </li>
54 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
55in a <tt>Function</tt></a> </li>
56 <li><a href="#iterate_convert">Turning an iterator into a
57class pointer</a> </li>
58 <li><a href="#iterate_complex">Finding call sites: a more
59complex example</a> </li>
60 <li><a href="#calls_and_invokes">Treating calls and invokes
61the same way</a> </li>
62 <li><a href="#iterate_chains">Iterating over def-use &amp;
63use-def chains</a> </li>
64 </ul>
65 </li>
66 <li><a href="#simplechanges">Making simple changes</a>
67 <ul>
68 <li><a href="#schanges_creating">Creating and inserting new
69 <tt>Instruction</tt>s</a> </li>
70 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
71 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
72with another <tt>Value</tt></a> </li>
73 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +000074 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +000075<!--
76 <li>Working with the Control Flow Graph
77 <ul>
78 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
79 <li>
80 <li>
81 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +000082-->
Chris Lattner261efe92003-11-25 01:02:51 +000083 </ul>
84 </li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +000085
86 <li><a href="#advanced">Advanced Topics</a>
87 <ul>
Chris Lattnerf1b200b2005-04-23 17:27:36 +000088 <li><a href="#TypeResolve">LLVM Type Resolution</a>
89 <ul>
90 <li><a href="#BuildRecType">Basic Recursive Type Construction</a></li>
91 <li><a href="#refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a></li>
92 <li><a href="#PATypeHolder">The PATypeHolder Class</a></li>
93 <li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
94 </ul></li>
95
Chris Lattnerd9d6e102005-04-23 16:10:52 +000096 <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
97 </ul></li>
98
Joel Stanley9b96c442002-09-06 21:55:13 +000099 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000100 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000101 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000102 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000103 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000104 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000105 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
106 <ul>
107 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
108 </ul>
109 </li>
110 <li><a href="#Module">The <tt>Module</tt> class</a></li>
111 <li><a href="#Constant">The <tt>Constant</tt> class</a>
112 <ul>
113 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
114 <ul>
115 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
116 <li><a href="#Function">The <tt>Function</tt> class</a></li>
117 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
118 </ul>
119 </li>
120 </ul>
121 </li>
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000122 </ul>
123 </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000124 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer096603a2004-05-26 08:41:35 +0000125 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000126 </ul>
127 </li>
128 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000129 </li>
Chris Lattner9355b472002-09-06 02:50:58 +0000130</ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000131
Chris Lattner69bf8a92004-05-23 21:06:58 +0000132<div class="doc_author">
133 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner94c43592004-05-26 16:52:55 +0000134 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
135 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
136 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000137</div>
138
Chris Lattner9355b472002-09-06 02:50:58 +0000139<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000140<div class="doc_section">
141 <a name="introduction">Introduction </a>
142</div>
Chris Lattner9355b472002-09-06 02:50:58 +0000143<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000144
145<div class="doc_text">
146
147<p>This document is meant to highlight some of the important classes and
Chris Lattner261efe92003-11-25 01:02:51 +0000148interfaces available in the LLVM source-base. This manual is not
149intended to explain what LLVM is, how it works, and what LLVM code looks
150like. It assumes that you know the basics of LLVM and are interested
151in writing transformations or otherwise analyzing or manipulating the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000152code.</p>
153
154<p>This document should get you oriented so that you can find your
Chris Lattner261efe92003-11-25 01:02:51 +0000155way in the continuously growing source code that makes up the LLVM
156infrastructure. Note that this manual is not intended to serve as a
157replacement for reading the source code, so if you think there should be
158a method in one of these classes to do something, but it's not listed,
159check the source. Links to the <a href="/doxygen/">doxygen</a> sources
160are provided to make this as easy as possible.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000161
162<p>The first section of this document describes general information that is
163useful to know when working in the LLVM infrastructure, and the second describes
164the Core LLVM classes. In the future this manual will be extended with
165information describing how to use extension libraries, such as dominator
166information, CFG traversal routines, and useful utilities like the <tt><a
167href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
168
169</div>
170
Chris Lattner9355b472002-09-06 02:50:58 +0000171<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000172<div class="doc_section">
173 <a name="general">General Information</a>
174</div>
175<!-- *********************************************************************** -->
176
177<div class="doc_text">
178
179<p>This section contains general information that is useful if you are working
180in the LLVM source-base, but that isn't specific to any particular API.</p>
181
182</div>
183
184<!-- ======================================================================= -->
185<div class="doc_subsection">
186 <a name="stl">The C++ Standard Template Library</a>
187</div>
188
189<div class="doc_text">
190
191<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner261efe92003-11-25 01:02:51 +0000192perhaps much more than you are used to, or have seen before. Because of
193this, you might want to do a little background reading in the
194techniques used and capabilities of the library. There are many good
195pages that discuss the STL, and several books on the subject that you
Misha Brukman13fd15c2004-01-15 00:14:41 +0000196can get, so it will not be discussed in this document.</p>
197
198<p>Here are some useful links:</p>
199
200<ol>
201
202<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
203reference</a> - an excellent reference for the STL and other parts of the
204standard C++ library.</li>
205
206<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Tanya Lattner09cf73c2004-06-22 04:24:55 +0000207O'Reilly book in the making. It has a decent
208Standard Library
209Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
Misha Brukman13fd15c2004-01-15 00:14:41 +0000210published.</li>
211
212<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
213Questions</a></li>
214
215<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
216Contains a useful <a
217href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
218STL</a>.</li>
219
220<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
221Page</a></li>
222
Tanya Lattner79445ba2004-12-08 18:34:56 +0000223<li><a href="http://64.78.49.204/">
Reid Spencer096603a2004-05-26 08:41:35 +0000224Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
225the book).</a></li>
226
Misha Brukman13fd15c2004-01-15 00:14:41 +0000227</ol>
228
229<p>You are also encouraged to take a look at the <a
230href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
231to write maintainable code more than where to put your curly braces.</p>
232
233</div>
234
235<!-- ======================================================================= -->
236<div class="doc_subsection">
237 <a name="stl">Other useful references</a>
238</div>
239
240<div class="doc_text">
241
Misha Brukman13fd15c2004-01-15 00:14:41 +0000242<ol>
243<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner261efe92003-11-25 01:02:51 +0000244Branch and Tag Primer</a></li>
Misha Brukmana0f71e42004-06-18 18:39:00 +0000245<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
246static and shared libraries across platforms</a></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000247</ol>
248
249</div>
250
Chris Lattner9355b472002-09-06 02:50:58 +0000251<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000252<div class="doc_section">
253 <a name="apis">Important and useful LLVM APIs</a>
254</div>
255<!-- *********************************************************************** -->
256
257<div class="doc_text">
258
259<p>Here we highlight some LLVM APIs that are generally useful and good to
260know about when writing transformations.</p>
261
262</div>
263
264<!-- ======================================================================= -->
265<div class="doc_subsection">
266 <a name="isa">The isa&lt;&gt;, cast&lt;&gt; and dyn_cast&lt;&gt; templates</a>
267</div>
268
269<div class="doc_text">
270
271<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner261efe92003-11-25 01:02:51 +0000272These templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
273operator, but they don't have some drawbacks (primarily stemming from
274the fact that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that
275have a v-table). Because they are used so often, you must know what they
276do and how they work. All of these templates are defined in the <a
277 href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000278file (note that you very rarely have to include this file directly).</p>
279
280<dl>
281 <dt><tt>isa&lt;&gt;</tt>: </dt>
282
283 <dd>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
284 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
285 a reference or pointer points to an instance of the specified class. This can
286 be very useful for constraint checking of various sorts (example below).</dd>
287
288 <dt><tt>cast&lt;&gt;</tt>: </dt>
289
290 <dd>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
291 converts a pointer or reference from a base class to a derived cast, causing
292 an assertion failure if it is not really an instance of the right type. This
293 should be used in cases where you have some information that makes you believe
294 that something is of the right type. An example of the <tt>isa&lt;&gt;</tt>
295 and <tt>cast&lt;&gt;</tt> template is:
296
Chris Lattner69bf8a92004-05-23 21:06:58 +0000297 <pre>
298 static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
299 if (isa&lt;<a href="#Constant">Constant</a>&gt;(V) || isa&lt;<a href="#Argument">Argument</a>&gt;(V) || isa&lt;<a href="#GlobalValue">GlobalValue</a>&gt;(V))
300 return true;
301
Chris Lattner53f72b32005-04-22 04:49:59 +0000302 <i>// Otherwise, it must be an instruction...</i>
303 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
304 }
Chris Lattner69bf8a92004-05-23 21:06:58 +0000305 </pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000306
307 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
308 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
309 operator.</p>
310
311 </dd>
312
313 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
314
315 <dd>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation. It
316 checks to see if the operand is of the specified type, and if so, returns a
317 pointer to it (this operator does not work with references). If the operand is
318 not of the correct type, a null pointer is returned. Thus, this works very
319 much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
320 same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt> operator is used
321 in an <tt>if</tt> statement or some other flow control statement like this:
322
Chris Lattner69bf8a92004-05-23 21:06:58 +0000323 <pre>
324 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
325 ...
326 }
327 </pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000328
329 <p> This form of the <tt>if</tt> statement effectively combines together a
330 call to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
331 statement, which is very convenient.</p>
332
Misha Brukman13fd15c2004-01-15 00:14:41 +0000333 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
334 <tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
335 In particular you should not use big chained <tt>if/then/else</tt> blocks to
336 check for lots of different variants of classes. If you find yourself
337 wanting to do this, it is much cleaner and more efficient to use the
Chris Lattner53f72b32005-04-22 04:49:59 +0000338 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000339
Chris Lattner261efe92003-11-25 01:02:51 +0000340 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000341
Chris Lattner261efe92003-11-25 01:02:51 +0000342 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000343
344 <dd>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
345 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as
346 an argument (which it then propagates). This can sometimes be useful,
347 allowing you to combine several null checks into one.</dd>
348
Chris Lattner261efe92003-11-25 01:02:51 +0000349 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000350
351 <dd>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
352 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
353 as an argument (which it then propagates). This can sometimes be useful,
354 allowing you to combine several null checks into one.</dd>
355
Chris Lattner261efe92003-11-25 01:02:51 +0000356 </dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000357
358<p>These five templates can be used with any classes, whether they have a
359v-table or not. To add support for these templates, you simply need to add
360<tt>classof</tt> static methods to the class you are interested casting
361to. Describing this is currently outside the scope of this document, but there
362are lots of examples in the LLVM source base.</p>
363
364</div>
365
366<!-- ======================================================================= -->
367<div class="doc_subsection">
368 <a name="DEBUG">The <tt>DEBUG()</tt> macro &amp; <tt>-debug</tt> option</a>
369</div>
370
371<div class="doc_text">
372
373<p>Often when working on your pass you will put a bunch of debugging printouts
374and other code into your pass. After you get it working, you want to remove
375it... but you may need it again in the future (to work out new bugs that you run
376across).</p>
377
378<p> Naturally, because of this, you don't want to delete the debug printouts,
379but you don't want them to always be noisy. A standard compromise is to comment
380them out, allowing you to enable them if you need them in the future.</p>
381
382<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
383file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
384this problem. Basically, you can put arbitrary code into the argument of the
385<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
386tool) is run with the '<tt>-debug</tt>' command line argument:</p>
387
Chris Lattner261efe92003-11-25 01:02:51 +0000388 <pre> ... <br> DEBUG(std::cerr &lt;&lt; "I am here!\n");<br> ...<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000389
390<p>Then you can run your pass like this:</p>
391
Chris Lattner261efe92003-11-25 01:02:51 +0000392 <pre> $ opt &lt; a.bc &gt; /dev/null -mypass<br> &lt;no output&gt;<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug<br> I am here!<br> $<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000393
394<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
395to not have to create "yet another" command line option for the debug output for
396your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
397so they do not cause a performance impact at all (for the same reason, they
398should also not contain side-effects!).</p>
399
400<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
401enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
402"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
403program hasn't been started yet, you can always just run it with
404<tt>-debug</tt>.</p>
405
406</div>
407
408<!-- _______________________________________________________________________ -->
409<div class="doc_subsubsection">
410 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
411 the <tt>-debug-only</tt> option</a>
412</div>
413
414<div class="doc_text">
415
416<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
417just turns on <b>too much</b> information (such as when working on the code
418generator). If you want to enable debug information with more fine-grained
419control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
420option as follows:</p>
421
Chris Lattner261efe92003-11-25 01:02:51 +0000422 <pre> ...<br> DEBUG(std::cerr &lt;&lt; "No debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "foo"<br> DEBUG(std::cerr &lt;&lt; "'foo' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "bar"<br> DEBUG(std::cerr &lt;&lt; "'bar' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE ""<br> DEBUG(std::cerr &lt;&lt; "No debug type (2)\n");<br> ...<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000423
424<p>Then you can run your pass like this:</p>
425
Chris Lattner261efe92003-11-25 01:02:51 +0000426 <pre> $ opt &lt; a.bc &gt; /dev/null -mypass<br> &lt;no output&gt;<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug<br> No debug type<br> 'foo' debug type<br> 'bar' debug type<br> No debug type (2)<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo<br> 'foo' debug type<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar<br> 'bar' debug type<br> $<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000427
428<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
429a file, to specify the debug type for the entire module (if you do this before
430you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
431<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
432"bar", because there is no system in place to ensure that names do not
433conflict. If two different modules use the same string, they will all be turned
434on when the name is specified. This allows, for example, all debug information
435for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000436even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000437
438</div>
439
440<!-- ======================================================================= -->
441<div class="doc_subsection">
442 <a name="Statistic">The <tt>Statistic</tt> template &amp; <tt>-stats</tt>
443 option</a>
444</div>
445
446<div class="doc_text">
447
448<p>The "<tt><a
449href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
450provides a template named <tt>Statistic</tt> that is used as a unified way to
451keep track of what the LLVM compiler is doing and how effective various
452optimizations are. It is useful to see what optimizations are contributing to
453making a particular program run faster.</p>
454
455<p>Often you may run your pass on some big program, and you're interested to see
456how many times it makes a certain transformation. Although you can do this with
457hand inspection, or some ad-hoc method, this is a real pain and not very useful
458for big programs. Using the <tt>Statistic</tt> template makes it very easy to
459keep track of this information, and the calculated information is presented in a
460uniform manner with the rest of the passes being executed.</p>
461
462<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
463it are as follows:</p>
464
465<ol>
Chris Lattner261efe92003-11-25 01:02:51 +0000466 <li>Define your statistic like this:
Chris Lattner261efe92003-11-25 01:02:51 +0000467 <pre>static Statistic&lt;&gt; NumXForms("mypassname", "The # of times I did stuff");<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000468
469 <p>The <tt>Statistic</tt> template can emulate just about any data-type,
470 but if you do not specify a template argument, it defaults to acting like
471 an unsigned int counter (this is usually what you want).</p></li>
472
Chris Lattner261efe92003-11-25 01:02:51 +0000473 <li>Whenever you make a transformation, bump the counter:
Chris Lattner261efe92003-11-25 01:02:51 +0000474 <pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner261efe92003-11-25 01:02:51 +0000475 </li>
476 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000477
478 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
479 statistics gathered, use the '<tt>-stats</tt>' option:</p>
480
Chris Lattner261efe92003-11-25 01:02:51 +0000481 <pre> $ opt -stats -mypassname &lt; program.bc &gt; /dev/null<br> ... statistic output ...<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000482
Chris Lattner261efe92003-11-25 01:02:51 +0000483 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
484suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000485
Chris Lattner261efe92003-11-25 01:02:51 +0000486 <pre> 7646 bytecodewriter - Number of normal instructions<br> 725 bytecodewriter - Number of oversized instructions<br> 129996 bytecodewriter - Number of bytecode bytes written<br> 2817 raise - Number of insts DCEd or constprop'd<br> 3213 raise - Number of cast-of-self removed<br> 5046 raise - Number of expression trees converted<br> 75 raise - Number of other getelementptr's formed<br> 138 raise - Number of load/store peepholes<br> 42 deadtypeelim - Number of unused typenames removed from symtab<br> 392 funcresolve - Number of varargs functions resolved<br> 27 globaldce - Number of global variables removed<br> 2 adce - Number of basic blocks removed<br> 134 cee - Number of branches revectored<br> 49 cee - Number of setcc instruction eliminated<br> 532 gcse - Number of loads removed<br> 2919 gcse - Number of instructions removed<br> 86 indvars - Number of canonical indvars added<br> 87 indvars - Number of aux indvars removed<br> 25 instcombine - Number of dead inst eliminate<br> 434 instcombine - Number of insts combined<br> 248 licm - Number of load insts hoisted<br> 1298 licm - Number of insts hoisted to a loop pre-header<br> 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)<br> 75 mem2reg - Number of alloca's promoted<br> 1444 cfgsimplify - Number of blocks simplified<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000487
488<p>Obviously, with so many optimizations, having a unified framework for this
489stuff is very nice. Making your pass fit well into the framework makes it more
490maintainable and useful.</p>
491
492</div>
493
494<!-- *********************************************************************** -->
495<div class="doc_section">
496 <a name="common">Helpful Hints for Common Operations</a>
497</div>
498<!-- *********************************************************************** -->
499
500<div class="doc_text">
501
502<p>This section describes how to perform some very simple transformations of
503LLVM code. This is meant to give examples of common idioms used, showing the
504practical side of LLVM transformations. <p> Because this is a "how-to" section,
505you should also read about the main classes that you will be working with. The
506<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
507and descriptions of the main classes that you should know about.</p>
508
509</div>
510
511<!-- NOTE: this section should be heavy on example code -->
512<!-- ======================================================================= -->
513<div class="doc_subsection">
514 <a name="inspection">Basic Inspection and Traversal Routines</a>
515</div>
516
517<div class="doc_text">
518
519<p>The LLVM compiler infrastructure have many different data structures that may
520be traversed. Following the example of the C++ standard template library, the
521techniques used to traverse these various data structures are all basically the
522same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
523method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
524function returns an iterator pointing to one past the last valid element of the
525sequence, and there is some <tt>XXXiterator</tt> data type that is common
526between the two operations.</p>
527
528<p>Because the pattern for iteration is common across many different aspects of
529the program representation, the standard template library algorithms may be used
530on them, and it is easier to remember how to iterate. First we show a few common
531examples of the data structures that need to be traversed. Other data
532structures are traversed in very similar ways.</p>
533
534</div>
535
536<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000537<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000538 <a name="iterate_function">Iterating over the </a><a
539 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
540 href="#Function"><tt>Function</tt></a>
541</div>
542
543<div class="doc_text">
544
545<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
546transform in some way; in particular, you'd like to manipulate its
547<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
548the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
549an example that prints the name of a <tt>BasicBlock</tt> and the number of
550<tt>Instruction</tt>s it contains:</p>
551
Chris Lattner261efe92003-11-25 01:02:51 +0000552 <pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> cerr &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has " <br> &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";<br> }<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000553
554<p>Note that i can be used as if it were a pointer for the purposes of
Joel Stanley9b96c442002-09-06 21:55:13 +0000555invoking member functions of the <tt>Instruction</tt> class. This is
556because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000557classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000558exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
559
560</div>
561
562<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000563<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000564 <a name="iterate_basicblock">Iterating over the </a><a
565 href="#Instruction"><tt>Instruction</tt></a>s in a <a
566 href="#BasicBlock"><tt>BasicBlock</tt></a>
567</div>
568
569<div class="doc_text">
570
571<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
572easy to iterate over the individual instructions that make up
573<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
574a <tt>BasicBlock</tt>:</p>
575
Chris Lattner55c04612005-03-06 06:00:13 +0000576<pre>
577 // blk is a pointer to a BasicBlock instance
578 for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
579 // the next statement works since operator&lt;&lt;(ostream&amp;,...)
580 // is overloaded for Instruction&amp;
581 std::cerr &lt;&lt; *i &lt;&lt; "\n";
582</pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000583
584<p>However, this isn't really the best way to print out the contents of a
585<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
586anything you'll care about, you could have just invoked the print routine on the
Chris Lattner55c04612005-03-06 06:00:13 +0000587basic block itself: <tt>std::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000588
589</div>
590
591<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000592<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000593 <a name="iterate_institer">Iterating over the </a><a
594 href="#Instruction"><tt>Instruction</tt></a>s in a <a
595 href="#Function"><tt>Function</tt></a>
596</div>
597
598<div class="doc_text">
599
600<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
601<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
602<tt>InstIterator</tt> should be used instead. You'll need to include <a
603href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
604and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000605small example that shows how to dump all instructions in a function to the standard error stream:<p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000606
Chris Lattner69bf8a92004-05-23 21:06:58 +0000607 <pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> cerr &lt;&lt; *i &lt;&lt; "\n";<br></pre>
Joel Stanleye7be6502002-09-09 15:50:33 +0000608Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
609worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000610initialize a worklist to contain all instructions in a <tt>Function</tt>
611F, all you would need to do is something like:
612 <pre>std::set&lt;Instruction*&gt; worklist;<br>worklist.insert(inst_begin(F), inst_end(F));<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000613
614<p>The STL set <tt>worklist</tt> would now contain all instructions in the
615<tt>Function</tt> pointed to by F.</p>
616
617</div>
618
619<!-- _______________________________________________________________________ -->
620<div class="doc_subsubsection">
621 <a name="iterate_convert">Turning an iterator into a class pointer (and
622 vice-versa)</a>
623</div>
624
625<div class="doc_text">
626
627<p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
Joel Stanley9b96c442002-09-06 21:55:13 +0000628instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000629a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000630Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000631is a <tt>BasicBlock::const_iterator</tt>:</p>
632
Chris Lattner261efe92003-11-25 01:02:51 +0000633 <pre> Instruction&amp; inst = *i; // grab reference to instruction reference<br> Instruction* pinst = &amp;*i; // grab pointer to instruction reference<br> const Instruction&amp; inst = *j;<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000634
635<p>However, the iterators you'll be working with in the LLVM framework are
636special: they will automatically convert to a ptr-to-instance type whenever they
637need to. Instead of dereferencing the iterator and then taking the address of
638the result, you can simply assign the iterator to the proper pointer type and
639you get the dereference and address-of operation as a result of the assignment
640(behind the scenes, this is a result of overloading casting mechanisms). Thus
641the last line of the last example,</p>
642
Chris Lattner261efe92003-11-25 01:02:51 +0000643 <pre>Instruction* pinst = &amp;*i;</pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000644
645<p>is semantically equivalent to</p>
646
Chris Lattner261efe92003-11-25 01:02:51 +0000647 <pre>Instruction* pinst = i;</pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000648
Chris Lattner69bf8a92004-05-23 21:06:58 +0000649<p>It's also possible to turn a class pointer into the corresponding iterator,
650and this is a constant time operation (very efficient). The following code
651snippet illustrates use of the conversion constructors provided by LLVM
652iterators. By using these, you can explicitly grab the iterator of something
653without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000654
Chris Lattner261efe92003-11-25 01:02:51 +0000655 <pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after *inst.<br> if (it != inst-&gt;getParent()-&gt;end()) cerr &lt;&lt; *it &lt;&lt; "\n";<br>}<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000656
Misha Brukman13fd15c2004-01-15 00:14:41 +0000657</div>
658
659<!--_______________________________________________________________________-->
660<div class="doc_subsubsection">
661 <a name="iterate_complex">Finding call sites: a slightly more complex
662 example</a>
663</div>
664
665<div class="doc_text">
666
667<p>Say that you're writing a FunctionPass and would like to count all the
668locations in the entire module (that is, across every <tt>Function</tt>) where a
669certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
670learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000671much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000672you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
673is what we want to do:</p>
674
Chris Lattner261efe92003-11-25 01:02:51 +0000675 <pre>initialize callCounter to zero<br>for each Function f in the Module<br> for each BasicBlock b in f<br> for each Instruction i in b<br> if (i is a CallInst and calls the given function)<br> increment callCounter<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000676
677<p>And the actual code is (remember, since we're writing a
678<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
679override the <tt>runOnFunction</tt> method...):</p>
680
Chris Lattner261efe92003-11-25 01:02:51 +0000681 <pre>Function* targetFunc = ...;<br><br>class OurFunctionPass : public FunctionPass {<br> public:<br> OurFunctionPass(): callCounter(0) { }<br><br> virtual runOnFunction(Function&amp; F) {<br> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {<br> for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {<br> if (<a
682 href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
683 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {<br> // we know we've encountered a call instruction, so we<br> // need to determine if it's a call to the<br> // function pointed to by m_func or not.<br> <br> if (callInst-&gt;getCalledFunction() == targetFunc)<br> ++callCounter;<br> }<br> }<br> }<br> <br> private:<br> unsigned callCounter;<br>};<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000684
685</div>
686
Brian Gaekef1972c62003-11-07 19:25:45 +0000687<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000688<div class="doc_subsubsection">
689 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
690</div>
691
692<div class="doc_text">
693
694<p>You may have noticed that the previous example was a bit oversimplified in
695that it did not deal with call sites generated by 'invoke' instructions. In
696this, and in other situations, you may find that you want to treat
697<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
698most-specific common base class is <tt>Instruction</tt>, which includes lots of
699less closely-related things. For these cases, LLVM provides a handy wrapper
700class called <a
Misha Brukman384047f2004-06-03 23:29:12 +0000701href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000702It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
703methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000704<tt>InvokeInst</tt>s.</p>
705
Chris Lattner69bf8a92004-05-23 21:06:58 +0000706<p>This class has "value semantics": it should be passed by value, not by
707reference and it should not be dynamically allocated or deallocated using
708<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
709assignable and constructable, with costs equivalents to that of a bare pointer.
710If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000711
712</div>
713
Chris Lattner1a3105b2002-09-09 05:49:39 +0000714<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000715<div class="doc_subsubsection">
716 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
717</div>
718
719<div class="doc_text">
720
721<p>Frequently, we might have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000722href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
723determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
724<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
725For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
726particular function <tt>foo</tt>. Finding all of the instructions that
727<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
728of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000729
Chris Lattner261efe92003-11-25 01:02:51 +0000730 <pre>Function* F = ...;<br><br>for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i) {<br> if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {<br> cerr &lt;&lt; "F is used in instruction:\n";<br> cerr &lt;&lt; *Inst &lt;&lt; "\n";<br> }<br>}<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000731
732<p>Alternately, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000733href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000734<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
735<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
736<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
737all of the values that a particular instruction uses (that is, the operands of
738the particular <tt>Instruction</tt>):</p>
739
Chris Lattner261efe92003-11-25 01:02:51 +0000740 <pre>Instruction* pi = ...;<br><br>for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {<br> Value* v = *i;<br> ...<br>}<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000741
Chris Lattner1a3105b2002-09-09 05:49:39 +0000742<!--
743 def-use chains ("finding all users of"): Value::use_begin/use_end
744 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman13fd15c2004-01-15 00:14:41 +0000745-->
746
747</div>
748
749<!-- ======================================================================= -->
750<div class="doc_subsection">
751 <a name="simplechanges">Making simple changes</a>
752</div>
753
754<div class="doc_text">
755
756<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000757infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000758transformations, it's fairly common to manipulate the contents of basic
759blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000760and gives example code.</p>
761
762</div>
763
Chris Lattner261efe92003-11-25 01:02:51 +0000764<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000765<div class="doc_subsubsection">
766 <a name="schanges_creating">Creating and inserting new
767 <tt>Instruction</tt>s</a>
768</div>
769
770<div class="doc_text">
771
772<p><i>Instantiating Instructions</i></p>
773
Chris Lattner69bf8a92004-05-23 21:06:58 +0000774<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000775constructor for the kind of instruction to instantiate and provide the necessary
776parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
777(const-ptr-to) <tt>Type</tt>. Thus:</p>
778
779<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
780
781<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
782one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
783subclass is likely to have varying default parameters which change the semantics
784of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000785href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000786Instruction</a> that you're interested in instantiating.</p>
787
788<p><i>Naming values</i></p>
789
790<p>It is very useful to name the values of instructions when you're able to, as
791this facilitates the debugging of your transformations. If you end up looking
792at generated LLVM machine code, you definitely want to have logical names
793associated with the results of instructions! By supplying a value for the
794<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
795associate a logical name with the result of the instruction's execution at
796runtime. For example, say that I'm writing a transformation that dynamically
797allocates space for an integer on the stack, and that integer is going to be
798used as some kind of index by some other code. To accomplish this, I place an
799<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
800<tt>Function</tt>, and I'm intending to use it within the same
801<tt>Function</tt>. I might do:</p>
802
803 <pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
804
805<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
806execution value, which is a pointer to an integer on the runtime stack.</p>
807
808<p><i>Inserting instructions</i></p>
809
810<p>There are essentially two ways to insert an <tt>Instruction</tt>
811into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
812
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000813<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000814 <li>Insertion into an explicit instruction list
815
816 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
817 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
818 before <tt>*pi</tt>, we do the following: </p>
819
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000820 <pre> BasicBlock *pb = ...;<br> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb-&gt;getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre>
821
822 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
823 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
824 classes provide constructors which take a pointer to a
825 <tt>BasicBlock</tt> to be appended to. For example code that
826 looked like: </p>
827
828 <pre> BasicBlock *pb = ...;<br> Instruction *newInst = new Instruction(...);<br> pb-&gt;getInstList().push_back(newInst); // appends newInst to pb<br></pre>
829
830 <p>becomes: </p>
831
832 <pre> BasicBlock *pb = ...;<br> Instruction *newInst = new Instruction(..., pb);<br></pre>
833
834 <p>which is much cleaner, especially if you are creating
835 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000836
837 <li>Insertion into an implicit instruction list
838
839 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
840 are implicitly associated with an existing instruction list: the instruction
841 list of the enclosing basic block. Thus, we could have accomplished the same
842 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
843 </p>
844
845 <pre> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);<br></pre>
846
847 <p>In fact, this sequence of steps occurs so frequently that the
848 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
849 constructors which take (as a default parameter) a pointer to an
850 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
851 precede. That is, <tt>Instruction</tt> constructors are capable of
852 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
853 provided instruction, immediately before that instruction. Using an
854 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
855 parameter, the above code becomes:</p>
856
857 <pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
858
859 <p>which is much cleaner, especially if you're creating a lot of
860instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
861</ul>
862
863</div>
864
865<!--_______________________________________________________________________-->
866<div class="doc_subsubsection">
867 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
868</div>
869
870<div class="doc_text">
871
872<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000873<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman13fd15c2004-01-15 00:14:41 +0000874you must have a pointer to the instruction that you wish to delete. Second, you
875need to obtain the pointer to that instruction's basic block. You use the
876pointer to the basic block to get its list of instructions and then use the
877erase function to remove your instruction. For example:</p>
878
Chris Lattner261efe92003-11-25 01:02:51 +0000879 <pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
880 href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();<br> BB-&gt;getInstList().erase(I);<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000881
882</div>
883
884<!--_______________________________________________________________________-->
885<div class="doc_subsubsection">
886 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
887 <tt>Value</tt></a>
888</div>
889
890<div class="doc_text">
891
892<p><i>Replacing individual instructions</i></p>
893
894<p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
Chris Lattner261efe92003-11-25 01:02:51 +0000895permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000896and <tt>ReplaceInstWithInst</tt>.</p>
897
Chris Lattner261efe92003-11-25 01:02:51 +0000898<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000899
Chris Lattner261efe92003-11-25 01:02:51 +0000900<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000901 <li><tt>ReplaceInstWithValue</tt>
902
903 <p>This function replaces all uses (within a basic block) of a given
904 instruction with a value, and then removes the original instruction. The
905 following example illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000906 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000907 pointer to an integer.</p>
908
909 <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
910
911 <li><tt>ReplaceInstWithInst</tt>
912
913 <p>This function replaces a particular instruction with another
914 instruction. The following example illustrates the replacement of one
915 <tt>AllocaInst</tt> with another.</p>
916
917 <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,<br> new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));<br></pre></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000918</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000919
920<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
921
922<p>You can use <tt>Value::replaceAllUsesWith</tt> and
923<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Misha Brukman384047f2004-06-03 23:29:12 +0000924doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
925and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000926information.</p>
927
928<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
929include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
930ReplaceInstWithValue, ReplaceInstWithInst -->
931
932</div>
933
Chris Lattner9355b472002-09-06 02:50:58 +0000934<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000935<div class="doc_section">
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000936 <a name="advanced">Advanced Topics</a>
937</div>
938<!-- *********************************************************************** -->
939
940<div class="doc_text">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000941<p>
942This section describes some of the advanced or obscure API's that most clients
943do not need to be aware of. These API's tend manage the inner workings of the
944LLVM system, and only need to be accessed in unusual circumstances.
945</p>
946</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000947
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000948<!-- ======================================================================= -->
949<div class="doc_subsection">
950 <a name="TypeResolve">LLVM Type Resolution</a>
951</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000952
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000953<div class="doc_text">
954
955<p>
956The LLVM type system has a very simple goal: allow clients to compare types for
957structural equality with a simple pointer comparison (aka a shallow compare).
958This goal makes clients much simpler and faster, and is used throughout the LLVM
959system.
960</p>
961
962<p>
963Unfortunately achieving this goal is not a simple matter. In particular,
964recursive types and late resolution of opaque types makes the situation very
965difficult to handle. Fortunately, for the most part, our implementation makes
966most clients able to be completely unaware of the nasty internal details. The
967primary case where clients are exposed to the inner workings of it are when
968building a recursive type. In addition to this case, the LLVM bytecode reader,
969assembly parser, and linker also have to be aware of the inner workings of this
970system.
971</p>
972
973</div>
974
975<!-- ______________________________________________________________________ -->
976<div class="doc_subsubsection">
977 <a name="BuildRecType">Basic Recursive Type Construction</a>
978</div>
979
980<div class="doc_text">
981
982<p>
983Because the most common question is "how do I build a recursive type with LLVM",
984we answer it now and explain it as we go. Here we include enough to cause this
985to be emitted to an output .ll file:
986</p>
987
988<pre>
989 %mylist = type { %mylist*, int }
990</pre>
991
992<p>
993To build this, use the following LLVM APIs:
994</p>
995
996<pre>
997 //<i> Create the initial outer struct.</i>
998 <a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
999 std::vector&lt;const Type*&gt; Elts;
1000 Elts.push_back(PointerType::get(StructTy));
1001 Elts.push_back(Type::IntTy);
1002 StructType *NewSTy = StructType::get(Elts);
1003
1004 //<i> At this point, NewSTy = "{ opaque*, int }". Tell VMCore that</i>
1005 //<i> the struct and the opaque type are actually the same.</i>
1006 cast&lt;OpaqueType&gt;(StructTy.get())-&gt;<a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
1007
1008 // <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
1009 // <i>kept up-to-date.</i>
1010 NewSTy = cast&lt;StructType&gt;(StructTy.get());
1011
1012 // <i>Add a name for the type to the module symbol table (optional).</i>
1013 MyModule-&gt;addTypeName("mylist", NewSTy);
1014</pre>
1015
1016<p>
1017This code shows the basic approach used to build recursive types: build a
1018non-recursive type using 'opaque', then use type unification to close the cycle.
1019The type unification step is performed by the <tt><a
1020ref="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
1021described next. After that, we describe the <a
1022href="#PATypeHolder">PATypeHolder class</a>.
1023</p>
1024
1025</div>
1026
1027<!-- ______________________________________________________________________ -->
1028<div class="doc_subsubsection">
1029 <a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
1030</div>
1031
1032<div class="doc_text">
1033<p>
1034The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
1035While this method is actually a member of the DerivedType class, it is most
1036often used on OpaqueType instances. Type unification is actually a recursive
1037process. After unification, types can become structurally isomorphic to
1038existing types, and all duplicates are deleted (to preserve pointer equality).
1039</p>
1040
1041<p>
1042In the example above, the OpaqueType object is definitely deleted.
1043Additionally, if there is an "{ \2*, int}" type already created in the system,
1044the pointer and struct type created are <b>also</b> deleted. Obviously whenever
1045a type is deleted, any "Type*" pointers in the program are invalidated. As
1046such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
1047live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
1048types can never move or be deleted). To deal with this, the <a
1049href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
1050reference to a possibly refined type, and the <a
1051href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
1052complex datastructures.
1053</p>
1054
1055</div>
1056
1057<!-- ______________________________________________________________________ -->
1058<div class="doc_subsubsection">
1059 <a name="PATypeHolder">The PATypeHolder Class</a>
1060</div>
1061
1062<div class="doc_text">
1063<p>
1064PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
1065happily goes about nuking types that become isomorphic to existing types, it
1066automatically updates all PATypeHolder objects to point to the new type. In the
1067example above, this allows the code to maintain a pointer to the resultant
1068resolved recursive type, even though the Type*'s are potentially invalidated.
1069</p>
1070
1071<p>
1072PATypeHolder is an extremely light-weight object that uses a lazy union-find
1073implementation to update pointers. For example the pointer from a Value to its
1074Type is maintained by PATypeHolder objects.
1075</p>
1076
1077</div>
1078
1079<!-- ______________________________________________________________________ -->
1080<div class="doc_subsubsection">
1081 <a name="AbstractTypeUser">The AbstractTypeUser Class</a>
1082</div>
1083
1084<div class="doc_text">
1085
1086<p>
1087Some data structures need more to perform more complex updates when types get
1088resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
1089move and potentially merge type planes in its representation when a pointer
1090changes.</p>
1091
1092<p>
1093To support this, a class can derive from the AbstractTypeUser class. This class
1094allows it to get callbacks when certain types are resolved. To register to get
1095callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
1096methods can be called on a type. Note that these methods only work for {\em
1097abstract} types. Concrete types (those that do not include an opaque objects
1098somewhere) can never be refined.
1099</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +00001100</div>
1101
1102
1103<!-- ======================================================================= -->
1104<div class="doc_subsection">
1105 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
1106</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +00001107
Chris Lattnerd9d6e102005-04-23 16:10:52 +00001108<div class="doc_text">
1109<p>This class provides a symbol table that the <a
1110href="#Function"><tt>Function</tt></a> and <a href="#Module">
1111<tt>Module</tt></a> classes use for naming definitions. The symbol table can
1112provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
1113href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
1114type. It hides the data it contains and provides access to it through a
1115controlled interface.</p>
1116
1117<p>Note that the symbol table class is should not be directly accessed by most
1118clients. It should only be used when iteration over the symbol table names
1119themselves are required, which is very special purpose. Note that not all LLVM
1120<a href="#Value">Value</a>s have names, and those without names (i.e. they have
1121an empty name) do not exist in the symbol table.
1122</p>
1123
1124<p>To use the <tt>SymbolTable</tt> well, you need to understand the
1125structure of the information it holds. The class contains two
1126<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
1127<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
1128The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
1129are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
1130however, are stored in a single dimension and accessed only by name.</p>
1131
1132<p>The interface of this class provides three basic types of operations:
1133<ol>
1134 <li><em>Accessors</em>. Accessors provide read-only access to information
1135 such as finding a value for a name with the
1136 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1137 <li><em>Mutators</em>. Mutators allow the user to add information to the
1138 <tt>SymbolTable</tt> with methods like
1139 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1140 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1141 of the symbol table in well defined ways, such as the method
1142 <a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
1143</ol>
1144
1145<h3>Accessors</h3>
1146<dl>
1147 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
1148 </dt>
1149 <dd>The <tt>lookup</tt> method searches the type plane given by the
1150 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1151 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1152
1153 <dt><tt>Type* lookupType( const std::string&amp; name) const</tt>:</dt>
1154 <dd>The <tt>lookupType</tt> method searches through the types for a
1155 <tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
1156 is not found, null is returned.</dd>
1157
1158 <dt><tt>bool hasTypes() const</tt>:</dt>
1159 <dd>This function returns true if an entry has been made into the type
1160 map.</dd>
1161
1162 <dt><tt>bool isEmpty() const</tt>:</dt>
1163 <dd>This function returns true if both the value and types maps are
1164 empty</dd>
1165</dl>
1166
1167<h3>Mutators</h3>
1168<dl>
1169 <dt><tt>void insert(Value *Val)</tt>:</dt>
1170 <dd>This method adds the provided value to the symbol table. The Value must
1171 have both a name and a type which are extracted and used to place the value
1172 in the correct type plane under the value's name.</dd>
1173
1174 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1175 <dd> Inserts a constant or type into the symbol table with the specified
1176 name. There can be a many to one mapping between names and constants
1177 or types.</dd>
1178
1179 <dt><tt>void insert(const std::string&amp; Name, Type *Typ)</tt>:</dt>
1180 <dd> Inserts a type into the symbol table with the specified name. There
1181 can be a many-to-one mapping between names and types. This method
1182 allows a type with an existing entry in the symbol table to get
1183 a new name.</dd>
1184
1185 <dt><tt>void remove(Value* Val)</tt>:</dt>
1186 <dd> This method removes a named value from the symbol table. The
1187 type and name of the Value are extracted from \p N and used to
1188 lookup the Value in the correct type plane. If the Value is
1189 not in the symbol table, this method silently ignores the
1190 request.</dd>
1191
1192 <dt><tt>void remove(Type* Typ)</tt>:</dt>
1193 <dd> This method removes a named type from the symbol table. The
1194 name of the type is extracted from \P T and used to look up
1195 the Type in the type map. If the Type is not in the symbol
1196 table, this method silently ignores the request.</dd>
1197
1198 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1199 <dd> Remove a constant or type with the specified name from the
1200 symbol table.</dd>
1201
1202 <dt><tt>Type* remove(const std::string&amp; Name, Type* T)</tt>:</dt>
1203 <dd> Remove a type with the specified name from the symbol table.
1204 Returns the removed Type.</dd>
1205
1206 <dt><tt>Value *value_remove(const value_iterator&amp; It)</tt>:</dt>
1207 <dd> Removes a specific value from the symbol table.
1208 Returns the removed value.</dd>
1209
1210 <dt><tt>bool strip()</tt>:</dt>
1211 <dd> This method will strip the symbol table of its names leaving
1212 the type and values. </dd>
1213
1214 <dt><tt>void clear()</tt>:</dt>
1215 <dd>Empty the symbol table completely.</dd>
1216</dl>
1217
1218<h3>Iteration</h3>
1219<p>The following functions describe three types of iterators you can obtain
1220the beginning or end of the sequence for both const and non-const. It is
1221important to keep track of the different kinds of iterators. There are
1222three idioms worth pointing out:</p>
1223<table>
1224 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1225 <tr>
1226 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1227 <td align="left"><pre><tt>
1228for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1229 PE = ST.plane_end(); PI != PE; ++PI ) {
1230 PI-&gt;first // This is the Type* of the plane
1231 PI-&gt;second // This is the SymbolTable::ValueMap of name/Value pairs
1232 </tt></pre></td>
1233 </tr>
1234 <tr>
1235 <td align="left">All name/Type Pairs</td><td>TI</td>
1236 <td align="left"><pre><tt>
1237for (SymbolTable::type_const_iterator TI = ST.type_begin(),
1238 TE = ST.type_end(); TI != TE; ++TI )
1239 TI-&gt;first // This is the name of the type
1240 TI-&gt;second // This is the Type* value associated with the name
1241 </tt></pre></td>
1242 </tr>
1243 <tr>
1244 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1245 <td align="left"><pre><tt>
1246for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
1247 VE = ST.value_end(SomeType); VI != VE; ++VI )
1248 VI-&gt;first // This is the name of the Value
1249 VI-&gt;second // This is the Value* value associated with the name
1250 </tt></pre></td>
1251 </tr>
1252</table>
1253
1254<p>Using the recommended iterator names and idioms will help you avoid
1255making mistakes. Of particular note, make sure that whenever you use
1256value_begin(SomeType) that you always compare the resulting iterator
1257with value_end(SomeType) not value_end(SomeOtherType) or else you
1258will loop infinitely.</p>
1259
1260<dl>
1261
1262 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1263 <dd>Get an iterator that starts at the beginning of the type planes.
1264 The iterator will iterate over the Type/ValueMap pairs in the
1265 type planes. </dd>
1266
1267 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1268 <dd>Get a const_iterator that starts at the beginning of the type
1269 planes. The iterator will iterate over the Type/ValueMap pairs
1270 in the type planes. </dd>
1271
1272 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1273 <dd>Get an iterator at the end of the type planes. This serves as
1274 the marker for end of iteration over the type planes.</dd>
1275
1276 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1277 <dd>Get a const_iterator at the end of the type planes. This serves as
1278 the marker for end of iteration over the type planes.</dd>
1279
1280 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
1281 <dd>Get an iterator that starts at the beginning of a type plane.
1282 The iterator will iterate over the name/value pairs in the type plane.
1283 Note: The type plane must already exist before using this.</dd>
1284
1285 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
1286 <dd>Get a const_iterator that starts at the beginning of a type plane.
1287 The iterator will iterate over the name/value pairs in the type plane.
1288 Note: The type plane must already exist before using this.</dd>
1289
1290 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
1291 <dd>Get an iterator to the end of a type plane. This serves as the marker
1292 for end of iteration of the type plane.
1293 Note: The type plane must already exist before using this.</dd>
1294
1295 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
1296 <dd>Get a const_iterator to the end of a type plane. This serves as the
1297 marker for end of iteration of the type plane.
1298 Note: the type plane must already exist before using this.</dd>
1299
1300 <dt><tt>type_iterator type_begin()</tt>:</dt>
1301 <dd>Get an iterator to the start of the name/Type map.</dd>
1302
1303 <dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
1304 <dd> Get a const_iterator to the start of the name/Type map.</dd>
1305
1306 <dt><tt>type_iterator type_end()</tt>:</dt>
1307 <dd>Get an iterator to the end of the name/Type map. This serves as the
1308 marker for end of iteration of the types.</dd>
1309
1310 <dt><tt>type_const_iterator type_end() const</tt>:</dt>
1311 <dd>Get a const-iterator to the end of the name/Type map. This serves
1312 as the marker for end of iteration of the types.</dd>
1313
1314 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
1315 <dd>This method returns a plane_const_iterator for iteration over
1316 the type planes starting at a specific plane, given by \p Ty.</dd>
1317
1318 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
1319 <dd>This method returns a plane_iterator for iteration over the
1320 type planes starting at a specific plane, given by \p Ty.</dd>
1321
1322</dl>
1323</div>
1324
1325
1326
1327<!-- *********************************************************************** -->
1328<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +00001329 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
1330</div>
1331<!-- *********************************************************************** -->
1332
1333<div class="doc_text">
1334
1335<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +00001336being inspected or transformed. The core LLVM classes are defined in
1337header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +00001338the <tt>lib/VMCore</tt> directory.</p>
1339
1340</div>
1341
1342<!-- ======================================================================= -->
1343<div class="doc_subsection">
1344 <a name="Value">The <tt>Value</tt> class</a>
1345</div>
1346
1347<div>
1348
1349<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
1350<br>
Misha Brukman384047f2004-06-03 23:29:12 +00001351doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001352
1353<p>The <tt>Value</tt> class is the most important class in the LLVM Source
1354base. It represents a typed value that may be used (among other things) as an
1355operand to an instruction. There are many different types of <tt>Value</tt>s,
1356such as <a href="#Constant"><tt>Constant</tt></a>s,<a
1357href="#Argument"><tt>Argument</tt></a>s. Even <a
1358href="#Instruction"><tt>Instruction</tt></a>s and <a
1359href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
1360
1361<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
1362for a program. For example, an incoming argument to a function (represented
1363with an instance of the <a href="#Argument">Argument</a> class) is "used" by
1364every instruction in the function that references the argument. To keep track
1365of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
1366href="#User"><tt>User</tt></a>s that is using it (the <a
1367href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
1368graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
1369def-use information in the program, and is accessible through the <tt>use_</tt>*
1370methods, shown below.</p>
1371
1372<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
1373and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
1374method. In addition, all LLVM values can be named. The "name" of the
1375<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
1376
Chris Lattner261efe92003-11-25 01:02:51 +00001377 <pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001378
1379<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
1380that the name of any value may be missing (an empty string), so names should
1381<b>ONLY</b> be used for debugging (making the source code easier to read,
1382debugging printouts), they should not be used to keep track of values or map
1383between them. For this purpose, use a <tt>std::map</tt> of pointers to the
1384<tt>Value</tt> itself instead.</p>
1385
1386<p>One important aspect of LLVM is that there is no distinction between an SSA
1387variable and the operation that produces it. Because of this, any reference to
1388the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +00001389argument, for example) is represented as a direct pointer to the instance of
1390the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +00001391represents this value. Although this may take some getting used to, it
1392simplifies the representation and makes it easier to manipulate.</p>
1393
1394</div>
1395
1396<!-- _______________________________________________________________________ -->
1397<div class="doc_subsubsection">
1398 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
1399</div>
1400
1401<div class="doc_text">
1402
Chris Lattner261efe92003-11-25 01:02:51 +00001403<ul>
1404 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
1405use-list<br>
1406 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
1407the use-list<br>
1408 <tt>unsigned use_size()</tt> - Returns the number of users of the
1409value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +00001410 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +00001411 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
1412the use-list.<br>
1413 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
1414use-list.<br>
1415 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
1416element in the list.
1417 <p> These methods are the interface to access the def-use
1418information in LLVM. As with all other iterators in LLVM, the naming
1419conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +00001420 </li>
1421 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001422 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +00001423 </li>
1424 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +00001425 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +00001426 <tt>void setName(const std::string &amp;Name)</tt>
1427 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
1428be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +00001429 </li>
1430 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001431
1432 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
1433 href="#User"><tt>User</tt>s</a> of the current value to refer to
1434 "<tt>V</tt>" instead. For example, if you detect that an instruction always
1435 produces a constant value (for example through constant folding), you can
1436 replace all uses of the instruction with the constant like this:</p>
1437
Chris Lattner261efe92003-11-25 01:02:51 +00001438 <pre> Inst-&gt;replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner261efe92003-11-25 01:02:51 +00001439</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001440
1441</div>
1442
1443<!-- ======================================================================= -->
1444<div class="doc_subsection">
1445 <a name="User">The <tt>User</tt> class</a>
1446</div>
1447
1448<div class="doc_text">
1449
1450<p>
1451<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +00001452doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001453Superclass: <a href="#Value"><tt>Value</tt></a></p>
1454
1455<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
1456refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1457that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1458referring to. The <tt>User</tt> class itself is a subclass of
1459<tt>Value</tt>.</p>
1460
1461<p>The operands of a <tt>User</tt> point directly to the LLVM <a
1462href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1463Single Assignment (SSA) form, there can only be one definition referred to,
1464allowing this direct connection. This connection provides the use-def
1465information in LLVM.</p>
1466
1467</div>
1468
1469<!-- _______________________________________________________________________ -->
1470<div class="doc_subsubsection">
1471 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
1472</div>
1473
1474<div class="doc_text">
1475
1476<p>The <tt>User</tt> class exposes the operand list in two ways: through
1477an index access interface and through an iterator based interface.</p>
1478
Chris Lattner261efe92003-11-25 01:02:51 +00001479<ul>
Chris Lattner261efe92003-11-25 01:02:51 +00001480 <li><tt>Value *getOperand(unsigned i)</tt><br>
1481 <tt>unsigned getNumOperands()</tt>
1482 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +00001483convenient form for direct access.</p></li>
1484
Chris Lattner261efe92003-11-25 01:02:51 +00001485 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
1486list<br>
Chris Lattner58360822005-01-17 00:12:04 +00001487 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
1488the operand list.<br>
1489 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +00001490operand list.
1491 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +00001492the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001493</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001494
1495</div>
1496
1497<!-- ======================================================================= -->
1498<div class="doc_subsection">
1499 <a name="Instruction">The <tt>Instruction</tt> class</a>
1500</div>
1501
1502<div class="doc_text">
1503
1504<p><tt>#include "</tt><tt><a
1505href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +00001506doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001507Superclasses: <a href="#User"><tt>User</tt></a>, <a
1508href="#Value"><tt>Value</tt></a></p>
1509
1510<p>The <tt>Instruction</tt> class is the common base class for all LLVM
1511instructions. It provides only a few methods, but is a very commonly used
1512class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1513opcode (instruction type) and the parent <a
1514href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1515into. To represent a specific type of instruction, one of many subclasses of
1516<tt>Instruction</tt> are used.</p>
1517
1518<p> Because the <tt>Instruction</tt> class subclasses the <a
1519href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1520way as for other <a href="#User"><tt>User</tt></a>s (with the
1521<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1522<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
1523the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
1524file contains some meta-data about the various different types of instructions
1525in LLVM. It describes the enum values that are used as opcodes (for example
1526<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
1527concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
1528example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1529href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1530this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +00001531<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001532
1533</div>
1534
1535<!-- _______________________________________________________________________ -->
1536<div class="doc_subsubsection">
1537 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
1538 class</a>
1539</div>
1540
1541<div class="doc_text">
1542
Chris Lattner261efe92003-11-25 01:02:51 +00001543<ul>
1544 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001545 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
1546this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001547 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001548 <p>Returns true if the instruction writes to memory, i.e. it is a
1549 <tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001550 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001551 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001552 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001553 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +00001554in all ways to the original except that the instruction has no parent
1555(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +00001556and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001557</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001558
1559</div>
1560
1561<!-- ======================================================================= -->
1562<div class="doc_subsection">
1563 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1564</div>
1565
1566<div class="doc_text">
1567
Misha Brukman384047f2004-06-03 23:29:12 +00001568<p><tt>#include "<a
1569href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
1570doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
1571Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001572Superclass: <a href="#Value"><tt>Value</tt></a></p>
1573
1574<p>This class represents a single entry multiple exit section of the code,
1575commonly known as a basic block by the compiler community. The
1576<tt>BasicBlock</tt> class maintains a list of <a
1577href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
1578Matching the language definition, the last element of this list of instructions
1579is always a terminator instruction (a subclass of the <a
1580href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
1581
1582<p>In addition to tracking the list of instructions that make up the block, the
1583<tt>BasicBlock</tt> class also keeps track of the <a
1584href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
1585
1586<p>Note that <tt>BasicBlock</tt>s themselves are <a
1587href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1588like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1589<tt>label</tt>.</p>
1590
1591</div>
1592
1593<!-- _______________________________________________________________________ -->
1594<div class="doc_subsubsection">
1595 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
1596 class</a>
1597</div>
1598
1599<div class="doc_text">
1600
Chris Lattner261efe92003-11-25 01:02:51 +00001601<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +00001602
1603<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +00001604 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +00001605
1606<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1607insertion into a function. The constructor optionally takes a name for the new
1608block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
1609the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
1610automatically inserted at the end of the specified <a
1611href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1612manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
1613
1614<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1615<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1616<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +00001617<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +00001618STL-style functions for accessing the instruction list.
1619
1620<p>These methods and typedefs are forwarding functions that have the same
1621semantics as the standard library methods of the same names. These methods
1622expose the underlying instruction list of a basic block in a way that is easy to
1623manipulate. To get the full complement of container operations (including
1624operations to update the list), you must use the <tt>getInstList()</tt>
1625method.</p></li>
1626
1627<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
1628
1629<p>This method is used to get access to the underlying container that actually
1630holds the Instructions. This method must be used when there isn't a forwarding
1631function in the <tt>BasicBlock</tt> class for the operation that you would like
1632to perform. Because there are no forwarding functions for "updating"
1633operations, you need to use this if you want to update the contents of a
1634<tt>BasicBlock</tt>.</p></li>
1635
1636<li><tt><a href="#Function">Function</a> *getParent()</tt>
1637
1638<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1639embedded into, or a null pointer if it is homeless.</p></li>
1640
1641<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
1642
1643<p> Returns a pointer to the terminator instruction that appears at the end of
1644the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1645instruction in the block is not a terminator, then a null pointer is
1646returned.</p></li>
1647
Chris Lattner261efe92003-11-25 01:02:51 +00001648</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001649
1650</div>
1651
1652<!-- ======================================================================= -->
1653<div class="doc_subsection">
1654 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1655</div>
1656
1657<div class="doc_text">
1658
1659<p><tt>#include "<a
1660href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +00001661doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
1662Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001663Superclasses: <a href="#User"><tt>User</tt></a>, <a
1664href="#Value"><tt>Value</tt></a></p>
1665
1666<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1667href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1668visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1669Because they are visible at global scope, they are also subject to linking with
1670other globals defined in different translation units. To control the linking
1671process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1672<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +00001673defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001674
1675<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1676<tt>static</tt> in C), it is not visible to code outside the current translation
1677unit, and does not participate in linking. If it has external linkage, it is
1678visible to external code, and does participate in linking. In addition to
1679linkage information, <tt>GlobalValue</tt>s keep track of which <a
1680href="#Module"><tt>Module</tt></a> they are currently part of.</p>
1681
1682<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
1683by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
1684global is always a pointer to its contents. It is important to remember this
1685when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
1686be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
1687subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
1688int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
1689the address of the first element of this array and the value of the
1690<tt>GlobalVariable</tt> are the same, they have different types. The
1691<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
1692is <tt>int.</tt> Because of this, accessing a global value requires you to
1693dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
1694can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
1695Language Reference Manual</a>.</p>
1696
1697</div>
1698
1699<!-- _______________________________________________________________________ -->
1700<div class="doc_subsubsection">
1701 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
1702 class</a>
1703</div>
1704
1705<div class="doc_text">
1706
Chris Lattner261efe92003-11-25 01:02:51 +00001707<ul>
1708 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +00001709 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +00001710 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
1711 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
1712 <p> </p>
1713 </li>
1714 <li><tt><a href="#Module">Module</a> *getParent()</tt>
1715 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +00001716GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001717</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001718
1719</div>
1720
1721<!-- ======================================================================= -->
1722<div class="doc_subsection">
1723 <a name="Function">The <tt>Function</tt> class</a>
1724</div>
1725
1726<div class="doc_text">
1727
1728<p><tt>#include "<a
1729href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +00001730info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
1731Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman13fd15c2004-01-15 00:14:41 +00001732href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
1733
1734<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
1735actually one of the more complex classes in the LLVM heirarchy because it must
1736keep track of a large amount of data. The <tt>Function</tt> class keeps track
1737of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
1738href="#Argument"><tt>Argument</tt></a>s, and a <a
1739href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
1740
1741<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
1742commonly used part of <tt>Function</tt> objects. The list imposes an implicit
1743ordering of the blocks in the function, which indicate how the code will be
1744layed out by the backend. Additionally, the first <a
1745href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1746<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
1747block. There are no implicit exit nodes, and in fact there may be multiple exit
1748nodes from a single <tt>Function</tt>. If the <a
1749href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1750the <tt>Function</tt> is actually a function declaration: the actual body of the
1751function hasn't been linked in yet.</p>
1752
1753<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1754<tt>Function</tt> class also keeps track of the list of formal <a
1755href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1756container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1757nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1758the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
1759
1760<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
1761LLVM feature that is only used when you have to look up a value by name. Aside
1762from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
1763internally to make sure that there are not conflicts between the names of <a
1764href="#Instruction"><tt>Instruction</tt></a>s, <a
1765href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1766href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
1767
Reid Spencer8b2da7a2004-07-18 13:10:31 +00001768<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
1769and therefore also a <a href="#Constant">Constant</a>. The value of the function
1770is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001771</div>
1772
1773<!-- _______________________________________________________________________ -->
1774<div class="doc_subsubsection">
1775 <a name="m_Function">Important Public Members of the <tt>Function</tt>
1776 class</a>
1777</div>
1778
1779<div class="doc_text">
1780
Chris Lattner261efe92003-11-25 01:02:51 +00001781<ul>
1782 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +00001783 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001784
1785 <p>Constructor used when you need to create new <tt>Function</tt>s to add
1786 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +00001787 create and what type of linkage the function should have. The <a
1788 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +00001789 specifies the formal arguments and return value for the function. The same
1790 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
1791 create multiple functions. The <tt>Parent</tt> argument specifies the Module
1792 in which the function is defined. If this argument is provided, the function
1793 will automatically be inserted into that module's list of
1794 functions.</p></li>
1795
Chris Lattner261efe92003-11-25 01:02:51 +00001796 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001797
1798 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
1799 function is "external", it does not have a body, and thus must be resolved
1800 by linking with a function defined in a different translation unit.</p></li>
1801
Chris Lattner261efe92003-11-25 01:02:51 +00001802 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +00001803 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001804
Chris Lattner77d69242005-03-15 05:19:20 +00001805 <tt>begin()</tt>, <tt>end()</tt>
1806 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001807
1808 <p>These are forwarding methods that make it easy to access the contents of
1809 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1810 list.</p></li>
1811
Chris Lattner261efe92003-11-25 01:02:51 +00001812 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001813
1814 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
1815 is necessary to use when you need to update the list or perform a complex
1816 action that doesn't have a forwarding method.</p></li>
1817
Chris Lattner89cc2652005-03-15 04:48:32 +00001818 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +00001819iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +00001820 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001821
Chris Lattner77d69242005-03-15 05:19:20 +00001822 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +00001823 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001824
1825 <p>These are forwarding methods that make it easy to access the contents of
1826 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
1827 list.</p></li>
1828
Chris Lattner261efe92003-11-25 01:02:51 +00001829 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001830
1831 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1832 necessary to use when you need to update the list or perform a complex
1833 action that doesn't have a forwarding method.</p></li>
1834
Chris Lattner261efe92003-11-25 01:02:51 +00001835 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001836
1837 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1838 function. Because the entry block for the function is always the first
1839 block, this returns the first block of the <tt>Function</tt>.</p></li>
1840
Chris Lattner261efe92003-11-25 01:02:51 +00001841 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1842 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001843
1844 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
1845 <tt>Function</tt> and returns the return type of the function, or the <a
1846 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
1847 function.</p></li>
1848
Chris Lattner261efe92003-11-25 01:02:51 +00001849 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001850
Chris Lattner261efe92003-11-25 01:02:51 +00001851 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001852 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001853</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001854
1855</div>
1856
1857<!-- ======================================================================= -->
1858<div class="doc_subsection">
1859 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1860</div>
1861
1862<div class="doc_text">
1863
1864<p><tt>#include "<a
1865href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
1866<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +00001867doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Misha Brukman13fd15c2004-01-15 00:14:41 +00001868Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1869href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
1870
1871<p>Global variables are represented with the (suprise suprise)
1872<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
1873subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
1874always referenced by their address (global values must live in memory, so their
1875"name" refers to their address). See <a
1876href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
1877may have an initial value (which must be a <a
1878href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
1879may be marked as "constant" themselves (indicating that their contents never
1880change at runtime).</p>
1881
1882</div>
1883
1884<!-- _______________________________________________________________________ -->
1885<div class="doc_subsubsection">
1886 <a name="m_GlobalVariable">Important Public Members of the
1887 <tt>GlobalVariable</tt> class</a>
1888</div>
1889
1890<div class="doc_text">
1891
Chris Lattner261efe92003-11-25 01:02:51 +00001892<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001893 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
1894 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
1895 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
1896
1897 <p>Create a new global variable of the specified type. If
1898 <tt>isConstant</tt> is true then the global variable will be marked as
1899 unchanging for the program. The Linkage parameter specifies the type of
1900 linkage (internal, external, weak, linkonce, appending) for the variable. If
1901 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
1902 the resultant global variable will have internal linkage. AppendingLinkage
1903 concatenates together all instances (in different translation units) of the
1904 variable into a single variable but is only applicable to arrays. &nbsp;See
1905 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
1906 further details on linkage types. Optionally an initializer, a name, and the
1907 module to put the variable into may be specified for the global variable as
1908 well.</p></li>
1909
Chris Lattner261efe92003-11-25 01:02:51 +00001910 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001911
1912 <p>Returns true if this is a global variable that is known not to
1913 be modified at runtime.</p></li>
1914
Chris Lattner261efe92003-11-25 01:02:51 +00001915 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001916
1917 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
1918
Chris Lattner261efe92003-11-25 01:02:51 +00001919 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001920
1921 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
1922 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001923</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001924
1925</div>
1926
1927<!-- ======================================================================= -->
1928<div class="doc_subsection">
1929 <a name="Module">The <tt>Module</tt> class</a>
1930</div>
1931
1932<div class="doc_text">
1933
1934<p><tt>#include "<a
1935href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +00001936<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001937
1938<p>The <tt>Module</tt> class represents the top level structure present in LLVM
1939programs. An LLVM module is effectively either a translation unit of the
1940original program or a combination of several translation units merged by the
1941linker. The <tt>Module</tt> class keeps track of a list of <a
1942href="#Function"><tt>Function</tt></a>s, a list of <a
1943href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1944href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1945helpful member functions that try to make common operations easy.</p>
1946
1947</div>
1948
1949<!-- _______________________________________________________________________ -->
1950<div class="doc_subsubsection">
1951 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
1952</div>
1953
1954<div class="doc_text">
1955
Chris Lattner261efe92003-11-25 01:02:51 +00001956<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001957 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +00001958</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001959
1960<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
1961provide a name for it (probably based on the name of the translation unit).</p>
1962
Chris Lattner261efe92003-11-25 01:02:51 +00001963<ul>
1964 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +00001965 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001966
Chris Lattner77d69242005-03-15 05:19:20 +00001967 <tt>begin()</tt>, <tt>end()</tt>
1968 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001969
1970 <p>These are forwarding methods that make it easy to access the contents of
1971 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1972 list.</p></li>
1973
Chris Lattner261efe92003-11-25 01:02:51 +00001974 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001975
1976 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1977 necessary to use when you need to update the list or perform a complex
1978 action that doesn't have a forwarding method.</p>
1979
1980 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00001981</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001982
1983<hr>
1984
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00001985<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +00001986 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001987
Chris Lattner89cc2652005-03-15 04:48:32 +00001988 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001989
Chris Lattner77d69242005-03-15 05:19:20 +00001990 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +00001991 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +00001992
1993 <p> These are forwarding methods that make it easy to access the contents of
1994 a <tt>Module</tt> object's <a
1995 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
1996
1997 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
1998
1999 <p>Returns the list of <a
2000 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2001 use when you need to update the list or perform a complex action that
2002 doesn't have a forwarding method.</p>
2003
2004 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00002005</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002006
2007<hr>
2008
2009<ul>
2010 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2011
2012 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2013 for this <tt>Module</tt>.</p>
2014
2015 <p><!-- Convenience methods --></p></li>
2016</ul>
2017
2018<hr>
2019
2020<ul>
2021 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2022 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2023
2024 <p>Look up the specified function in the <tt>Module</tt> <a
2025 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2026 <tt>null</tt>.</p></li>
2027
2028 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2029 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2030
2031 <p>Look up the specified function in the <tt>Module</tt> <a
2032 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2033 external declaration for the function and return it.</p></li>
2034
2035 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2036
2037 <p>If there is at least one entry in the <a
2038 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2039 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2040 string.</p></li>
2041
2042 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
2043 href="#Type">Type</a> *Ty)</tt>
2044
2045 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2046 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2047 name, true is returned and the <a
2048 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2049</ul>
2050
2051</div>
2052
2053<!-- ======================================================================= -->
2054<div class="doc_subsection">
2055 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2056</div>
2057
2058<div class="doc_text">
2059
2060<p>Constant represents a base class for different types of constants. It
2061is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
2062ConstantArray etc for representing the various types of Constants.</p>
2063
2064</div>
2065
2066<!-- _______________________________________________________________________ -->
2067<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002068 <a name="m_Constant">Important Public Methods</a>
2069</div>
2070<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +00002071</div>
2072
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002073<!-- _______________________________________________________________________ -->
2074<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002075<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00002076<ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002077 <li>ConstantSInt : This subclass of Constant represents a signed integer
2078 constant.
Chris Lattner261efe92003-11-25 01:02:51 +00002079 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002080 <li><tt>int64_t getValue() const</tt>: Returns the underlying value of
2081 this constant. </li>
Chris Lattner261efe92003-11-25 01:02:51 +00002082 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002083 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002084 <li>ConstantUInt : This class represents an unsigned integer.
2085 <ul>
2086 <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
2087 this constant. </li>
2088 </ul>
2089 </li>
2090 <li>ConstantFP : This class represents a floating point constant.
2091 <ul>
2092 <li><tt>double getValue() const</tt>: Returns the underlying value of
2093 this constant. </li>
2094 </ul>
2095 </li>
2096 <li>ConstantBool : This represents a boolean constant.
2097 <ul>
2098 <li><tt>bool getValue() const</tt>: Returns the underlying value of this
2099 constant. </li>
2100 </ul>
2101 </li>
2102 <li>ConstantArray : This represents a constant array.
2103 <ul>
2104 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +00002105 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002106 </ul>
2107 </li>
2108 <li>ConstantStruct : This represents a constant struct.
2109 <ul>
2110 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +00002111 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +00002112 </ul>
2113 </li>
2114 <li>GlobalValue : This represents either a global variable or a function. In
2115 either case, the value is a constant fixed address (after linking).
2116 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00002117</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002118</div>
2119
2120<!-- ======================================================================= -->
2121<div class="doc_subsection">
2122 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
2123</div>
2124
2125<div class="doc_text">
2126
2127<p>Type as noted earlier is also a subclass of a Value class. Any primitive
2128type (like int, short etc) in LLVM is an instance of Type Class. All other
2129types are instances of subclasses of type like FunctionType, ArrayType
2130etc. DerivedType is the interface for all such dervied types including
2131FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
2132be recursive (StructType). There exists exactly one instance of any type
2133structure at a time. This allows using pointer equality of Type *s for comparing
2134types.</p>
2135
2136</div>
2137
2138<!-- _______________________________________________________________________ -->
2139<div class="doc_subsubsection">
2140 <a name="m_Value">Important Public Methods</a>
2141</div>
2142
2143<div class="doc_text">
2144
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00002145<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002146
Misha Brukman13fd15c2004-01-15 00:14:41 +00002147 <li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
2148 is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
2149 not true for Float and Double. </li>
2150
2151 <li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
2152 unsigned. This is not quite the complement of isSigned... nonnumeric types
2153 return false as they do with isSigned. This returns true for UByteTy,
2154 UShortTy, UIntTy, and ULongTy. </li>
2155
Chris Lattner4573f1b2004-07-08 17:49:37 +00002156 <li><tt>bool isInteger() const</tt>: Equivalent to isSigned() || isUnsigned().</li>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002157
2158 <li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
2159 type, which is either Bool type or one of the Integer types.</li>
2160
2161 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
2162 floating point types.</li>
2163
Misha Brukman13fd15c2004-01-15 00:14:41 +00002164 <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
2165 this type can be converted to 'Ty' without any reinterpretation of bits. For
Chris Lattner69bf8a92004-05-23 21:06:58 +00002166 example, uint to int or one pointer type to another.</li>
Reid Spencerc7d1d822004-11-01 09:16:30 +00002167</ul>
2168</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002169
Reid Spencerc7d1d822004-11-01 09:16:30 +00002170<!-- _______________________________________________________________________ -->
2171<div class="doc_subsubsection">
2172 <a name="m_Value">Important Derived Types</a>
2173</div>
2174<div class="doc_text">
2175<ul>
2176 <li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner261efe92003-11-25 01:02:51 +00002177 <ul>
Reid Spencerc7d1d822004-11-01 09:16:30 +00002178 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2179 of the elements in the sequential type. </li>
2180 </ul>
2181 </li>
2182 <li>ArrayType : This is a subclass of SequentialType and defines interface for
2183 array types.
2184 <ul>
2185 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2186 elements in the array. </li>
2187 </ul>
2188 </li>
2189 <li>PointerType : Subclass of SequentialType for pointer types. </li>
2190 <li>StructType : subclass of DerivedTypes for struct types </li>
2191 <li>FunctionType : subclass of DerivedTypes for function types.
2192 <ul>
2193 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2194 function</li>
2195 <li><tt> const Type * getReturnType() const</tt>: Returns the
2196 return type of the function.</li>
2197 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2198 the type of the ith parameter.</li>
2199 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2200 number of formal parameters.</li>
Chris Lattner261efe92003-11-25 01:02:51 +00002201 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002202 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +00002203</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +00002204</div>
2205
2206<!-- ======================================================================= -->
2207<div class="doc_subsection">
2208 <a name="Argument">The <tt>Argument</tt> class</a>
2209</div>
2210
2211<div class="doc_text">
2212
2213<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +00002214arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +00002215arguments. An argument has a pointer to the parent Function.</p>
2216
2217</div>
2218
Chris Lattner9355b472002-09-06 02:50:58 +00002219<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +00002220<hr>
2221<address>
2222 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
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2226
2227 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2228 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
2229 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
2230 Last modified: $Date$
2231</address>
2232
Chris Lattner261efe92003-11-25 01:02:51 +00002233</body>
2234</html>
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