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4<head>
5 <title>LLVM Programmer's Manual</title>
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Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]7</head>
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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 +0000[diff] [blame]14<ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]15 <li><a href="#introduction">Introduction</a></li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]16 <li><a href="#general">General Information</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]17 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]18 <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 +0000[diff] [blame]23
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]24-->
Chris Lattner84b7f8d2003-08-01 22:20:59 +0000[diff] [blame]25 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]26 </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>
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]31 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]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>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]38 <li><a href="#Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]39option</a></li>
40<!--
41 <li>The <tt>InstVisitor</tt> template
42 <li>The general graph API
43-->
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]44 <li><a href="#ViewGraph">Viewing graphs while debugging code</a></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]45 </ul>
46 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]47 <li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]48 <ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]49 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
50 <ul>
51 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
52in a <tt>Function</tt></a> </li>
53 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
54in a <tt>BasicBlock</tt></a> </li>
55 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
56in a <tt>Function</tt></a> </li>
57 <li><a href="#iterate_convert">Turning an iterator into a
58class pointer</a> </li>
59 <li><a href="#iterate_complex">Finding call sites: a more
60complex example</a> </li>
61 <li><a href="#calls_and_invokes">Treating calls and invokes
62the same way</a> </li>
63 <li><a href="#iterate_chains">Iterating over def-use &amp;
64use-def chains</a> </li>
65 </ul>
66 </li>
67 <li><a href="#simplechanges">Making simple changes</a>
68 <ul>
69 <li><a href="#schanges_creating">Creating and inserting new
70 <tt>Instruction</tt>s</a> </li>
71 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
72 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
73with another <tt>Value</tt></a> </li>
74 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]75 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]76<!--
77 <li>Working with the Control Flow Graph
78 <ul>
79 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
80 <li>
81 <li>
82 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]83-->
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]84 </ul>
85 </li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]86
87 <li><a href="#advanced">Advanced Topics</a>
88 <ul>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]89 <li><a href="#TypeResolve">LLVM Type Resolution</a>
90 <ul>
91 <li><a href="#BuildRecType">Basic Recursive Type Construction</a></li>
92 <li><a href="#refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a></li>
93 <li><a href="#PATypeHolder">The PATypeHolder Class</a></li>
94 <li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
95 </ul></li>
96
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]97 <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
98 </ul></li>
99
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]100 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]101 <ul>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]102 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]103 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]104 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]105 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]106 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]107 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
108 <ul>
109 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
110 </ul>
111 </li>
112 <li><a href="#Module">The <tt>Module</tt> class</a></li>
113 <li><a href="#Constant">The <tt>Constant</tt> class</a>
114 <ul>
115 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
116 <ul>
117 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
118 <li><a href="#Function">The <tt>Function</tt> class</a></li>
119 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
120 </ul>
121 </li>
122 </ul>
123 </li>
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]124 </ul>
125 </li>
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]126 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]127 </ul>
128 </li>
129 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]130 </li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]131</ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]132
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]133<div class="doc_author">
134 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner94c43592004-05-26 16:52:55 +0000[diff] [blame]135 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
136 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
137 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]138</div>
139
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]140<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]141<div class="doc_section">
142 <a name="introduction">Introduction </a>
143</div>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]144<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]145
146<div class="doc_text">
147
148<p>This document is meant to highlight some of the important classes and
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]149interfaces available in the LLVM source-base. This manual is not
150intended to explain what LLVM is, how it works, and what LLVM code looks
151like. It assumes that you know the basics of LLVM and are interested
152in writing transformations or otherwise analyzing or manipulating the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]153code.</p>
154
155<p>This document should get you oriented so that you can find your
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]156way in the continuously growing source code that makes up the LLVM
157infrastructure. Note that this manual is not intended to serve as a
158replacement for reading the source code, so if you think there should be
159a method in one of these classes to do something, but it's not listed,
160check the source. Links to the <a href="/doxygen/">doxygen</a> sources
161are provided to make this as easy as possible.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]162
163<p>The first section of this document describes general information that is
164useful to know when working in the LLVM infrastructure, and the second describes
165the Core LLVM classes. In the future this manual will be extended with
166information describing how to use extension libraries, such as dominator
167information, CFG traversal routines, and useful utilities like the <tt><a
168href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
169
170</div>
171
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]172<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]173<div class="doc_section">
174 <a name="general">General Information</a>
175</div>
176<!-- *********************************************************************** -->
177
178<div class="doc_text">
179
180<p>This section contains general information that is useful if you are working
181in the LLVM source-base, but that isn't specific to any particular API.</p>
182
183</div>
184
185<!-- ======================================================================= -->
186<div class="doc_subsection">
187 <a name="stl">The C++ Standard Template Library</a>
188</div>
189
190<div class="doc_text">
191
192<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]193perhaps much more than you are used to, or have seen before. Because of
194this, you might want to do a little background reading in the
195techniques used and capabilities of the library. There are many good
196pages that discuss the STL, and several books on the subject that you
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]197can get, so it will not be discussed in this document.</p>
198
199<p>Here are some useful links:</p>
200
201<ol>
202
203<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
204reference</a> - an excellent reference for the STL and other parts of the
205standard C++ library.</li>
206
207<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Tanya Lattner09cf73c2004-06-22 04:24:55 +0000[diff] [blame]208O'Reilly book in the making. It has a decent
209Standard Library
210Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]211published.</li>
212
213<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
214Questions</a></li>
215
216<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
217Contains a useful <a
218href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
219STL</a>.</li>
220
221<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
222Page</a></li>
223
Tanya Lattner79445ba2004-12-08 18:34:56 +0000[diff] [blame]224<li><a href="http://64.78.49.204/">
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]225Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
226the book).</a></li>
227
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]228</ol>
229
230<p>You are also encouraged to take a look at the <a
231href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
232to write maintainable code more than where to put your curly braces.</p>
233
234</div>
235
236<!-- ======================================================================= -->
237<div class="doc_subsection">
238 <a name="stl">Other useful references</a>
239</div>
240
241<div class="doc_text">
242
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]243<ol>
244<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]245Branch and Tag Primer</a></li>
Misha Brukmana0f71e42004-06-18 18:39:00 +0000[diff] [blame]246<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
247static and shared libraries across platforms</a></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]248</ol>
249
250</div>
251
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]252<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]253<div class="doc_section">
254 <a name="apis">Important and useful LLVM APIs</a>
255</div>
256<!-- *********************************************************************** -->
257
258<div class="doc_text">
259
260<p>Here we highlight some LLVM APIs that are generally useful and good to
261know about when writing transformations.</p>
262
263</div>
264
265<!-- ======================================================================= -->
266<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]267 <a name="isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt> and
268 <tt>dyn_cast&lt;&gt;</tt> templates</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]269</div>
270
271<div class="doc_text">
272
273<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]274These templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
275operator, but they don't have some drawbacks (primarily stemming from
276the fact that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that
277have a v-table). Because they are used so often, you must know what they
278do and how they work. All of these templates are defined in the <a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]279 href="/doxygen/Casting_8h-source.html"><tt>llvm/Support/Casting.h</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]280file (note that you very rarely have to include this file directly).</p>
281
282<dl>
283 <dt><tt>isa&lt;&gt;</tt>: </dt>
284
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]285 <dd><p>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]286 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
287 a reference or pointer points to an instance of the specified class. This can
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]288 be very useful for constraint checking of various sorts (example below).</p>
289 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]290
291 <dt><tt>cast&lt;&gt;</tt>: </dt>
292
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]293 <dd><p>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]294 converts a pointer or reference from a base class to a derived cast, causing
295 an assertion failure if it is not really an instance of the right type. This
296 should be used in cases where you have some information that makes you believe
297 that something is of the right type. An example of the <tt>isa&lt;&gt;</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]298 and <tt>cast&lt;&gt;</tt> template is:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]299
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]300<div class="doc_code">
301<pre>
302static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
303 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))
304 return true;
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]305
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]306 // <i>Otherwise, it must be an instruction...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]307 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
308}
309</pre>
310</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]311
312 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
313 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
314 operator.</p>
315
316 </dd>
317
318 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
319
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]320 <dd><p>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation.
321 It checks to see if the operand is of the specified type, and if so, returns a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]322 pointer to it (this operator does not work with references). If the operand is
323 not of the correct type, a null pointer is returned. Thus, this works very
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]324 much like the <tt>dynamic_cast&lt;&gt;</tt> operator in C++, and should be
325 used in the same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt>
326 operator is used in an <tt>if</tt> statement or some other flow control
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]327 statement like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]328
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]329<div class="doc_code">
330<pre>
331if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]332 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]333}
334</pre>
335</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]336
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]337 <p>This form of the <tt>if</tt> statement effectively combines together a call
338 to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
339 statement, which is very convenient.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]340
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]341 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
342 <tt>dynamic_cast&lt;&gt;</tt> or Java's <tt>instanceof</tt> operator, can be
343 abused. In particular, you should not use big chained <tt>if/then/else</tt>
344 blocks to check for lots of different variants of classes. If you find
345 yourself wanting to do this, it is much cleaner and more efficient to use the
346 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]347
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]348 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]349
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]350 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
351
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]352 <dd><p>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]353 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as an
354 argument (which it then propagates). This can sometimes be useful, allowing
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]355 you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]356
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]357 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]358
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]359 <dd><p>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]360 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
361 as an argument (which it then propagates). This can sometimes be useful,
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]362 allowing you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]363
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]364</dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]365
366<p>These five templates can be used with any classes, whether they have a
367v-table or not. To add support for these templates, you simply need to add
368<tt>classof</tt> static methods to the class you are interested casting
369to. Describing this is currently outside the scope of this document, but there
370are lots of examples in the LLVM source base.</p>
371
372</div>
373
374<!-- ======================================================================= -->
375<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]376 <a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]377</div>
378
379<div class="doc_text">
380
381<p>Often when working on your pass you will put a bunch of debugging printouts
382and other code into your pass. After you get it working, you want to remove
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]383it, but you may need it again in the future (to work out new bugs that you run
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]384across).</p>
385
386<p> Naturally, because of this, you don't want to delete the debug printouts,
387but you don't want them to always be noisy. A standard compromise is to comment
388them out, allowing you to enable them if you need them in the future.</p>
389
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]390<p>The "<tt><a href="/doxygen/Debug_8h-source.html">llvm/Support/Debug.h</a></tt>"
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]391file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
392this problem. Basically, you can put arbitrary code into the argument of the
393<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
394tool) is run with the '<tt>-debug</tt>' command line argument:</p>
395
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]396<div class="doc_code">
397<pre>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]398DOUT &lt;&lt; "I am here!\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]399</pre>
400</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]401
402<p>Then you can run your pass like this:</p>
403
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]404<div class="doc_code">
405<pre>
406$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]407<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]408$ opt &lt; a.bc &gt; /dev/null -mypass -debug
409I am here!
410</pre>
411</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]412
413<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
414to not have to create "yet another" command line option for the debug output for
415your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
416so they do not cause a performance impact at all (for the same reason, they
417should also not contain side-effects!).</p>
418
419<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
420enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
421"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
422program hasn't been started yet, you can always just run it with
423<tt>-debug</tt>.</p>
424
425</div>
426
427<!-- _______________________________________________________________________ -->
428<div class="doc_subsubsection">
Chris Lattnerc9151082005-04-26 22:57:07 +0000[diff] [blame]429 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]430 the <tt>-debug-only</tt> option</a>
431</div>
432
433<div class="doc_text">
434
435<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
436just turns on <b>too much</b> information (such as when working on the code
437generator). If you want to enable debug information with more fine-grained
438control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
439option as follows:</p>
440
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]441<div class="doc_code">
442<pre>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]443DOUT &lt;&lt; "No debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]444#undef DEBUG_TYPE
445#define DEBUG_TYPE "foo"
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]446DOUT &lt;&lt; "'foo' debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]447#undef DEBUG_TYPE
448#define DEBUG_TYPE "bar"
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]449DOUT &lt;&lt; "'bar' debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]450#undef DEBUG_TYPE
451#define DEBUG_TYPE ""
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]452DOUT &lt;&lt; "No debug type (2)\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]453</pre>
454</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]455
456<p>Then you can run your pass like this:</p>
457
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]458<div class="doc_code">
459<pre>
460$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]461<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]462$ opt &lt; a.bc &gt; /dev/null -mypass -debug
463No debug type
464'foo' debug type
465'bar' debug type
466No debug type (2)
467$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo
468'foo' debug type
469$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar
470'bar' debug type
471</pre>
472</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]473
474<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
475a file, to specify the debug type for the entire module (if you do this before
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]476you <tt>#include "llvm/Support/Debug.h"</tt>, you don't have to insert the ugly
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]477<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
478"bar", because there is no system in place to ensure that names do not
479conflict. If two different modules use the same string, they will all be turned
480on when the name is specified. This allows, for example, all debug information
481for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]482even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]483
484</div>
485
486<!-- ======================================================================= -->
487<div class="doc_subsection">
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]488 <a name="Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]489 option</a>
490</div>
491
492<div class="doc_text">
493
494<p>The "<tt><a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]495href="/doxygen/Statistic_8h-source.html">llvm/ADT/Statistic.h</a></tt>" file
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]496provides a class named <tt>Statistic</tt> that is used as a unified way to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]497keep track of what the LLVM compiler is doing and how effective various
498optimizations are. It is useful to see what optimizations are contributing to
499making a particular program run faster.</p>
500
501<p>Often you may run your pass on some big program, and you're interested to see
502how many times it makes a certain transformation. Although you can do this with
503hand inspection, or some ad-hoc method, this is a real pain and not very useful
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]504for big programs. Using the <tt>Statistic</tt> class makes it very easy to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]505keep track of this information, and the calculated information is presented in a
506uniform manner with the rest of the passes being executed.</p>
507
508<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
509it are as follows:</p>
510
511<ol>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]512 <li><p>Define your statistic like this:</p>
513
514<div class="doc_code">
515<pre>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]516#define <a href="#DEBUG_TYPE">DEBUG_TYPE</a> "mypassname" <i>// This goes before any #includes.</i>
517STATISTIC(NumXForms, "The # of times I did stuff");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]518</pre>
519</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]520
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]521 <p>The <tt>STATISTIC</tt> macro defines a static variable, whose name is
522 specified by the first argument. The pass name is taken from the DEBUG_TYPE
523 macro, and the description is taken from the second argument. The variable
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]524 defined ("NumXForms" in this case) acts like an unsigned integer.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]525
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]526 <li><p>Whenever you make a transformation, bump the counter:</p>
527
528<div class="doc_code">
529<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]530++NumXForms; // <i>I did stuff!</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]531</pre>
532</div>
533
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]534 </li>
535 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]536
537 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
538 statistics gathered, use the '<tt>-stats</tt>' option:</p>
539
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]540<div class="doc_code">
541<pre>
542$ opt -stats -mypassname &lt; program.bc &gt; /dev/null
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]543<i>... statistics output ...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]544</pre>
545</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]546
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]547 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
548suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]549
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]550<div class="doc_code">
551<pre>
552 7646 bytecodewriter - Number of normal instructions
553 725 bytecodewriter - Number of oversized instructions
554 129996 bytecodewriter - Number of bytecode bytes written
555 2817 raise - Number of insts DCEd or constprop'd
556 3213 raise - Number of cast-of-self removed
557 5046 raise - Number of expression trees converted
558 75 raise - Number of other getelementptr's formed
559 138 raise - Number of load/store peepholes
560 42 deadtypeelim - Number of unused typenames removed from symtab
561 392 funcresolve - Number of varargs functions resolved
562 27 globaldce - Number of global variables removed
563 2 adce - Number of basic blocks removed
564 134 cee - Number of branches revectored
565 49 cee - Number of setcc instruction eliminated
566 532 gcse - Number of loads removed
567 2919 gcse - Number of instructions removed
568 86 indvars - Number of canonical indvars added
569 87 indvars - Number of aux indvars removed
570 25 instcombine - Number of dead inst eliminate
571 434 instcombine - Number of insts combined
572 248 licm - Number of load insts hoisted
573 1298 licm - Number of insts hoisted to a loop pre-header
574 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
575 75 mem2reg - Number of alloca's promoted
576 1444 cfgsimplify - Number of blocks simplified
577</pre>
578</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]579
580<p>Obviously, with so many optimizations, having a unified framework for this
581stuff is very nice. Making your pass fit well into the framework makes it more
582maintainable and useful.</p>
583
584</div>
585
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]586<!-- ======================================================================= -->
587<div class="doc_subsection">
588 <a name="ViewGraph">Viewing graphs while debugging code</a>
589</div>
590
591<div class="doc_text">
592
593<p>Several of the important data structures in LLVM are graphs: for example
594CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
595LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
596<a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
597DAGs</a>. In many cases, while debugging various parts of the compiler, it is
598nice to instantly visualize these graphs.</p>
599
600<p>LLVM provides several callbacks that are available in a debug build to do
601exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
602the current LLVM tool will pop up a window containing the CFG for the function
603where each basic block is a node in the graph, and each node contains the
604instructions in the block. Similarly, there also exists
605<tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
606<tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
607and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]608you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]609up a window. Alternatively, you can sprinkle calls to these functions in your
610code in places you want to debug.</p>
611
612<p>Getting this to work requires a small amount of configuration. On Unix
613systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
614toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
615Mac OS/X, download and install the Mac OS/X <a
616href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
617<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
618it) to your path. Once in your system and path are set up, rerun the LLVM
619configure script and rebuild LLVM to enable this functionality.</p>
620
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]621<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
622<i>interesting</i> nodes in large complex graphs. From gdb, if you
623<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
624next <tt>call DAG.viewGraph()</tt> would hilight the node in the
625specified color (choices of colors can be found at <a
626href="http://www.graphviz.org/doc/info/colors.html">Colors<a>.) More
627complex node attributes can be provided with <tt>call
628DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
629found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
630Attributes</a>.) If you want to restart and clear all the current graph
631attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
632
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]633</div>
634
635
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]636<!-- *********************************************************************** -->
637<div class="doc_section">
638 <a name="common">Helpful Hints for Common Operations</a>
639</div>
640<!-- *********************************************************************** -->
641
642<div class="doc_text">
643
644<p>This section describes how to perform some very simple transformations of
645LLVM code. This is meant to give examples of common idioms used, showing the
646practical side of LLVM transformations. <p> Because this is a "how-to" section,
647you should also read about the main classes that you will be working with. The
648<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
649and descriptions of the main classes that you should know about.</p>
650
651</div>
652
653<!-- NOTE: this section should be heavy on example code -->
654<!-- ======================================================================= -->
655<div class="doc_subsection">
656 <a name="inspection">Basic Inspection and Traversal Routines</a>
657</div>
658
659<div class="doc_text">
660
661<p>The LLVM compiler infrastructure have many different data structures that may
662be traversed. Following the example of the C++ standard template library, the
663techniques used to traverse these various data structures are all basically the
664same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
665method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
666function returns an iterator pointing to one past the last valid element of the
667sequence, and there is some <tt>XXXiterator</tt> data type that is common
668between the two operations.</p>
669
670<p>Because the pattern for iteration is common across many different aspects of
671the program representation, the standard template library algorithms may be used
672on them, and it is easier to remember how to iterate. First we show a few common
673examples of the data structures that need to be traversed. Other data
674structures are traversed in very similar ways.</p>
675
676</div>
677
678<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]679<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]680 <a name="iterate_function">Iterating over the </a><a
681 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
682 href="#Function"><tt>Function</tt></a>
683</div>
684
685<div class="doc_text">
686
687<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
688transform in some way; in particular, you'd like to manipulate its
689<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
690the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
691an example that prints the name of a <tt>BasicBlock</tt> and the number of
692<tt>Instruction</tt>s it contains:</p>
693
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]694<div class="doc_code">
695<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]696// <i>func is a pointer to a Function instance</i>
697for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i)
698 // <i>Print out the name of the basic block if it has one, and then the</i>
699 // <i>number of instructions that it contains</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]700 llvm::cerr &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has "
701 &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]702</pre>
703</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]704
705<p>Note that i can be used as if it were a pointer for the purposes of
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]706invoking member functions of the <tt>Instruction</tt> class. This is
707because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]708classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]709exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
710
711</div>
712
713<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]714<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]715 <a name="iterate_basicblock">Iterating over the </a><a
716 href="#Instruction"><tt>Instruction</tt></a>s in a <a
717 href="#BasicBlock"><tt>BasicBlock</tt></a>
718</div>
719
720<div class="doc_text">
721
722<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
723easy to iterate over the individual instructions that make up
724<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
725a <tt>BasicBlock</tt>:</p>
726
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]727<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]728<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]729// <i>blk is a pointer to a BasicBlock instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]730for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]731 // <i>The next statement works since operator&lt;&lt;(ostream&amp;,...)</i>
732 // <i>is overloaded for Instruction&amp;</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]733 llvm::cerr &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]734</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]735</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]736
737<p>However, this isn't really the best way to print out the contents of a
738<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
739anything you'll care about, you could have just invoked the print routine on the
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]740basic block itself: <tt>llvm::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]741
742</div>
743
744<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]745<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]746 <a name="iterate_institer">Iterating over the </a><a
747 href="#Instruction"><tt>Instruction</tt></a>s in a <a
748 href="#Function"><tt>Function</tt></a>
749</div>
750
751<div class="doc_text">
752
753<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
754<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
755<tt>InstIterator</tt> should be used instead. You'll need to include <a
756href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
757and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]758small example that shows how to dump all instructions in a function to the standard error stream:<p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]759
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]760<div class="doc_code">
761<pre>
762#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
763
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]764// <i>F is a ptr to a Function instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]765for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]766 llvm::cerr &lt;&lt; *i &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]767</pre>
768</div>
769
770<p>Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]771worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]772initialize a worklist to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]773F, all you would need to do is something like:</p>
774
775<div class="doc_code">
776<pre>
777std::set&lt;Instruction*&gt; worklist;
778worklist.insert(inst_begin(F), inst_end(F));
779</pre>
780</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]781
782<p>The STL set <tt>worklist</tt> would now contain all instructions in the
783<tt>Function</tt> pointed to by F.</p>
784
785</div>
786
787<!-- _______________________________________________________________________ -->
788<div class="doc_subsubsection">
789 <a name="iterate_convert">Turning an iterator into a class pointer (and
790 vice-versa)</a>
791</div>
792
793<div class="doc_text">
794
795<p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]796instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]797a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]798Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]799is a <tt>BasicBlock::const_iterator</tt>:</p>
800
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]801<div class="doc_code">
802<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]803Instruction&amp; inst = *i; // <i>Grab reference to instruction reference</i>
804Instruction* pinst = &amp;*i; // <i>Grab pointer to instruction reference</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]805const Instruction&amp; inst = *j;
806</pre>
807</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]808
809<p>However, the iterators you'll be working with in the LLVM framework are
810special: they will automatically convert to a ptr-to-instance type whenever they
811need to. Instead of dereferencing the iterator and then taking the address of
812the result, you can simply assign the iterator to the proper pointer type and
813you get the dereference and address-of operation as a result of the assignment
814(behind the scenes, this is a result of overloading casting mechanisms). Thus
815the last line of the last example,</p>
816
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]817<div class="doc_code">
818<pre>
819Instruction* pinst = &amp;*i;
820</pre>
821</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]822
823<p>is semantically equivalent to</p>
824
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]825<div class="doc_code">
826<pre>
827Instruction* pinst = i;
828</pre>
829</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]830
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]831<p>It's also possible to turn a class pointer into the corresponding iterator,
832and this is a constant time operation (very efficient). The following code
833snippet illustrates use of the conversion constructors provided by LLVM
834iterators. By using these, you can explicitly grab the iterator of something
835without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]836
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]837<div class="doc_code">
838<pre>
839void printNextInstruction(Instruction* inst) {
840 BasicBlock::iterator it(inst);
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]841 ++it; // <i>After this line, it refers to the instruction after *inst</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]842 if (it != inst-&gt;getParent()-&gt;end()) llvm::cerr &lt;&lt; *it &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]843}
844</pre>
845</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]846
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]847</div>
848
849<!--_______________________________________________________________________-->
850<div class="doc_subsubsection">
851 <a name="iterate_complex">Finding call sites: a slightly more complex
852 example</a>
853</div>
854
855<div class="doc_text">
856
857<p>Say that you're writing a FunctionPass and would like to count all the
858locations in the entire module (that is, across every <tt>Function</tt>) where a
859certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
860learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]861much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]862you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
863is what we want to do:</p>
864
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]865<div class="doc_code">
866<pre>
867initialize callCounter to zero
868for each Function f in the Module
869 for each BasicBlock b in f
870 for each Instruction i in b
871 if (i is a CallInst and calls the given function)
872 increment callCounter
873</pre>
874</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]875
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]876<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]877<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]878override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]879
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]880<div class="doc_code">
881<pre>
882Function* targetFunc = ...;
883
884class OurFunctionPass : public FunctionPass {
885 public:
886 OurFunctionPass(): callCounter(0) { }
887
888 virtual runOnFunction(Function&amp; F) {
889 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
890 for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
891 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
892 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]893 // <i>We know we've encountered a call instruction, so we</i>
894 // <i>need to determine if it's a call to the</i>
895 // <i>function pointed to by m_func or not</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]896
897 if (callInst-&gt;getCalledFunction() == targetFunc)
898 ++callCounter;
899 }
900 }
901 }
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]902 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]903
904 private:
905 unsigned callCounter;
906};
907</pre>
908</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]909
910</div>
911
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]912<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]913<div class="doc_subsubsection">
914 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
915</div>
916
917<div class="doc_text">
918
919<p>You may have noticed that the previous example was a bit oversimplified in
920that it did not deal with call sites generated by 'invoke' instructions. In
921this, and in other situations, you may find that you want to treat
922<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
923most-specific common base class is <tt>Instruction</tt>, which includes lots of
924less closely-related things. For these cases, LLVM provides a handy wrapper
925class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]926href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]927It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
928methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]929<tt>InvokeInst</tt>s.</p>
930
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]931<p>This class has "value semantics": it should be passed by value, not by
932reference and it should not be dynamically allocated or deallocated using
933<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
934assignable and constructable, with costs equivalents to that of a bare pointer.
935If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]936
937</div>
938
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]939<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]940<div class="doc_subsubsection">
941 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
942</div>
943
944<div class="doc_text">
945
946<p>Frequently, we might have an instance of the <a
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]947href="/doxygen/classllvm_1_1Value.html">Value Class</a> and we want to
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]948determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
949<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
950For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
951particular function <tt>foo</tt>. Finding all of the instructions that
952<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
953of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]954
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]955<div class="doc_code">
956<pre>
957Function* F = ...;
958
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]959for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i)
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]960 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]961 llvm::cerr &lt;&lt; "F is used in instruction:\n";
962 llvm::cerr &lt;&lt; *Inst &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]963 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]964</pre>
965</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]966
967<p>Alternately, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]968href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]969<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
970<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
971<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
972all of the values that a particular instruction uses (that is, the operands of
973the particular <tt>Instruction</tt>):</p>
974
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]975<div class="doc_code">
976<pre>
977Instruction* pi = ...;
978
979for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {
980 Value* v = *i;
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]981 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]982}
983</pre>
984</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]985
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]986<!--
987 def-use chains ("finding all users of"): Value::use_begin/use_end
988 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]989-->
990
991</div>
992
993<!-- ======================================================================= -->
994<div class="doc_subsection">
995 <a name="simplechanges">Making simple changes</a>
996</div>
997
998<div class="doc_text">
999
1000<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]1001infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1002transformations, it's fairly common to manipulate the contents of basic
1003blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1004and gives example code.</p>
1005
1006</div>
1007
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1008<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1009<div class="doc_subsubsection">
1010 <a name="schanges_creating">Creating and inserting new
1011 <tt>Instruction</tt>s</a>
1012</div>
1013
1014<div class="doc_text">
1015
1016<p><i>Instantiating Instructions</i></p>
1017
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1018<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1019constructor for the kind of instruction to instantiate and provide the necessary
1020parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
1021(const-ptr-to) <tt>Type</tt>. Thus:</p>
1022
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1023<div class="doc_code">
1024<pre>
1025AllocaInst* ai = new AllocaInst(Type::IntTy);
1026</pre>
1027</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1028
1029<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
1030one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
1031subclass is likely to have varying default parameters which change the semantics
1032of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1033href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1034Instruction</a> that you're interested in instantiating.</p>
1035
1036<p><i>Naming values</i></p>
1037
1038<p>It is very useful to name the values of instructions when you're able to, as
1039this facilitates the debugging of your transformations. If you end up looking
1040at generated LLVM machine code, you definitely want to have logical names
1041associated with the results of instructions! By supplying a value for the
1042<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
1043associate a logical name with the result of the instruction's execution at
1044runtime. For example, say that I'm writing a transformation that dynamically
1045allocates space for an integer on the stack, and that integer is going to be
1046used as some kind of index by some other code. To accomplish this, I place an
1047<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
1048<tt>Function</tt>, and I'm intending to use it within the same
1049<tt>Function</tt>. I might do:</p>
1050
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1051<div class="doc_code">
1052<pre>
1053AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");
1054</pre>
1055</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1056
1057<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
1058execution value, which is a pointer to an integer on the runtime stack.</p>
1059
1060<p><i>Inserting instructions</i></p>
1061
1062<p>There are essentially two ways to insert an <tt>Instruction</tt>
1063into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
1064
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]1065<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1066 <li>Insertion into an explicit instruction list
1067
1068 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
1069 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
1070 before <tt>*pi</tt>, we do the following: </p>
1071
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1072<div class="doc_code">
1073<pre>
1074BasicBlock *pb = ...;
1075Instruction *pi = ...;
1076Instruction *newInst = new Instruction(...);
1077
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1078pb-&gt;getInstList().insert(pi, newInst); // <i>Inserts newInst before pi in pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1079</pre>
1080</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1081
1082 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
1083 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
1084 classes provide constructors which take a pointer to a
1085 <tt>BasicBlock</tt> to be appended to. For example code that
1086 looked like: </p>
1087
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1088<div class="doc_code">
1089<pre>
1090BasicBlock *pb = ...;
1091Instruction *newInst = new Instruction(...);
1092
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1093pb-&gt;getInstList().push_back(newInst); // <i>Appends newInst to pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1094</pre>
1095</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1096
1097 <p>becomes: </p>
1098
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1099<div class="doc_code">
1100<pre>
1101BasicBlock *pb = ...;
1102Instruction *newInst = new Instruction(..., pb);
1103</pre>
1104</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1105
1106 <p>which is much cleaner, especially if you are creating
1107 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1108
1109 <li>Insertion into an implicit instruction list
1110
1111 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
1112 are implicitly associated with an existing instruction list: the instruction
1113 list of the enclosing basic block. Thus, we could have accomplished the same
1114 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
1115 </p>
1116
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1117<div class="doc_code">
1118<pre>
1119Instruction *pi = ...;
1120Instruction *newInst = new Instruction(...);
1121
1122pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);
1123</pre>
1124</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1125
1126 <p>In fact, this sequence of steps occurs so frequently that the
1127 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
1128 constructors which take (as a default parameter) a pointer to an
1129 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
1130 precede. That is, <tt>Instruction</tt> constructors are capable of
1131 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
1132 provided instruction, immediately before that instruction. Using an
1133 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
1134 parameter, the above code becomes:</p>
1135
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1136<div class="doc_code">
1137<pre>
1138Instruction* pi = ...;
1139Instruction* newInst = new Instruction(..., pi);
1140</pre>
1141</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1142
1143 <p>which is much cleaner, especially if you're creating a lot of
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1144 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1145</ul>
1146
1147</div>
1148
1149<!--_______________________________________________________________________-->
1150<div class="doc_subsubsection">
1151 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
1152</div>
1153
1154<div class="doc_text">
1155
1156<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1157<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1158you must have a pointer to the instruction that you wish to delete. Second, you
1159need to obtain the pointer to that instruction's basic block. You use the
1160pointer to the basic block to get its list of instructions and then use the
1161erase function to remove your instruction. For example:</p>
1162
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1163<div class="doc_code">
1164<pre>
1165<a href="#Instruction">Instruction</a> *I = .. ;
1166<a href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();
1167
1168BB-&gt;getInstList().erase(I);
1169</pre>
1170</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1171
1172</div>
1173
1174<!--_______________________________________________________________________-->
1175<div class="doc_subsubsection">
1176 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
1177 <tt>Value</tt></a>
1178</div>
1179
1180<div class="doc_text">
1181
1182<p><i>Replacing individual instructions</i></p>
1183
1184<p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1185permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1186and <tt>ReplaceInstWithInst</tt>.</p>
1187
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1188<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1189
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1190<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1191 <li><tt>ReplaceInstWithValue</tt>
1192
1193 <p>This function replaces all uses (within a basic block) of a given
1194 instruction with a value, and then removes the original instruction. The
1195 following example illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1196 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1197 pointer to an integer.</p>
1198
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1199<div class="doc_code">
1200<pre>
1201AllocaInst* instToReplace = ...;
1202BasicBlock::iterator ii(instToReplace);
1203
1204ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1205 Constant::getNullValue(PointerType::get(Type::IntTy)));
1206</pre></div></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1207
1208 <li><tt>ReplaceInstWithInst</tt>
1209
1210 <p>This function replaces a particular instruction with another
1211 instruction. The following example illustrates the replacement of one
1212 <tt>AllocaInst</tt> with another.</p>
1213
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1214<div class="doc_code">
1215<pre>
1216AllocaInst* instToReplace = ...;
1217BasicBlock::iterator ii(instToReplace);
1218
1219ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1220 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));
1221</pre></div></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1222</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1223
1224<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
1225
1226<p>You can use <tt>Value::replaceAllUsesWith</tt> and
1227<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]1228doxygen documentation for the <a href="/doxygen/classllvm_1_1Value.html">Value Class</a>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1229and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1230information.</p>
1231
1232<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
1233include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
1234ReplaceInstWithValue, ReplaceInstWithInst -->
1235
1236</div>
1237
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1238<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1239<div class="doc_section">
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1240 <a name="advanced">Advanced Topics</a>
1241</div>
1242<!-- *********************************************************************** -->
1243
1244<div class="doc_text">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1245<p>
1246This section describes some of the advanced or obscure API's that most clients
1247do not need to be aware of. These API's tend manage the inner workings of the
1248LLVM system, and only need to be accessed in unusual circumstances.
1249</p>
1250</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1251
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1252<!-- ======================================================================= -->
1253<div class="doc_subsection">
1254 <a name="TypeResolve">LLVM Type Resolution</a>
1255</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1256
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1257<div class="doc_text">
1258
1259<p>
1260The LLVM type system has a very simple goal: allow clients to compare types for
1261structural equality with a simple pointer comparison (aka a shallow compare).
1262This goal makes clients much simpler and faster, and is used throughout the LLVM
1263system.
1264</p>
1265
1266<p>
1267Unfortunately achieving this goal is not a simple matter. In particular,
1268recursive types and late resolution of opaque types makes the situation very
1269difficult to handle. Fortunately, for the most part, our implementation makes
1270most clients able to be completely unaware of the nasty internal details. The
1271primary case where clients are exposed to the inner workings of it are when
1272building a recursive type. In addition to this case, the LLVM bytecode reader,
1273assembly parser, and linker also have to be aware of the inner workings of this
1274system.
1275</p>
1276
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1277<p>
1278For our purposes below, we need three concepts. First, an "Opaque Type" is
1279exactly as defined in the <a href="LangRef.html#t_opaque">language
1280reference</a>. Second an "Abstract Type" is any type which includes an
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1281opaque type as part of its type graph (for example "<tt>{ opaque, i32 }</tt>").
1282Third, a concrete type is a type that is not an abstract type (e.g. "<tt>{ i32,
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1283float }</tt>").
1284</p>
1285
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1286</div>
1287
1288<!-- ______________________________________________________________________ -->
1289<div class="doc_subsubsection">
1290 <a name="BuildRecType">Basic Recursive Type Construction</a>
1291</div>
1292
1293<div class="doc_text">
1294
1295<p>
1296Because the most common question is "how do I build a recursive type with LLVM",
1297we answer it now and explain it as we go. Here we include enough to cause this
1298to be emitted to an output .ll file:
1299</p>
1300
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1301<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1302<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1303%mylist = type { %mylist*, i32 }
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1304</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1305</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1306
1307<p>
1308To build this, use the following LLVM APIs:
1309</p>
1310
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1311<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1312<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1313// <i>Create the initial outer struct</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1314<a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
1315std::vector&lt;const Type*&gt; Elts;
1316Elts.push_back(PointerType::get(StructTy));
1317Elts.push_back(Type::IntTy);
1318StructType *NewSTy = StructType::get(Elts);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1319
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1320// <i>At this point, NewSTy = "{ opaque*, i32 }". Tell VMCore that</i>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1321// <i>the struct and the opaque type are actually the same.</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1322cast&lt;OpaqueType&gt;(StructTy.get())-&gt;<a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1323
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1324// <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1325// <i>kept up-to-date</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1326NewSTy = cast&lt;StructType&gt;(StructTy.get());
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1327
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1328// <i>Add a name for the type to the module symbol table (optional)</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1329MyModule-&gt;addTypeName("mylist", NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1330</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1331</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1332
1333<p>
1334This code shows the basic approach used to build recursive types: build a
1335non-recursive type using 'opaque', then use type unification to close the cycle.
1336The type unification step is performed by the <tt><a
1337ref="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
1338described next. After that, we describe the <a
1339href="#PATypeHolder">PATypeHolder class</a>.
1340</p>
1341
1342</div>
1343
1344<!-- ______________________________________________________________________ -->
1345<div class="doc_subsubsection">
1346 <a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
1347</div>
1348
1349<div class="doc_text">
1350<p>
1351The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
1352While this method is actually a member of the DerivedType class, it is most
1353often used on OpaqueType instances. Type unification is actually a recursive
1354process. After unification, types can become structurally isomorphic to
1355existing types, and all duplicates are deleted (to preserve pointer equality).
1356</p>
1357
1358<p>
1359In the example above, the OpaqueType object is definitely deleted.
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1360Additionally, if there is an "{ \2*, i32}" type already created in the system,
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1361the pointer and struct type created are <b>also</b> deleted. Obviously whenever
1362a type is deleted, any "Type*" pointers in the program are invalidated. As
1363such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
1364live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
1365types can never move or be deleted). To deal with this, the <a
1366href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
1367reference to a possibly refined type, and the <a
1368href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
1369complex datastructures.
1370</p>
1371
1372</div>
1373
1374<!-- ______________________________________________________________________ -->
1375<div class="doc_subsubsection">
1376 <a name="PATypeHolder">The PATypeHolder Class</a>
1377</div>
1378
1379<div class="doc_text">
1380<p>
1381PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
1382happily goes about nuking types that become isomorphic to existing types, it
1383automatically updates all PATypeHolder objects to point to the new type. In the
1384example above, this allows the code to maintain a pointer to the resultant
1385resolved recursive type, even though the Type*'s are potentially invalidated.
1386</p>
1387
1388<p>
1389PATypeHolder is an extremely light-weight object that uses a lazy union-find
1390implementation to update pointers. For example the pointer from a Value to its
1391Type is maintained by PATypeHolder objects.
1392</p>
1393
1394</div>
1395
1396<!-- ______________________________________________________________________ -->
1397<div class="doc_subsubsection">
1398 <a name="AbstractTypeUser">The AbstractTypeUser Class</a>
1399</div>
1400
1401<div class="doc_text">
1402
1403<p>
1404Some data structures need more to perform more complex updates when types get
1405resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
1406move and potentially merge type planes in its representation when a pointer
1407changes.</p>
1408
1409<p>
1410To support this, a class can derive from the AbstractTypeUser class. This class
1411allows it to get callbacks when certain types are resolved. To register to get
1412callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1413methods can be called on a type. Note that these methods only work for <i>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1414 abstract</i> types. Concrete types (those that do not include any opaque
1415objects) can never be refined.
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1416</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1417</div>
1418
1419
1420<!-- ======================================================================= -->
1421<div class="doc_subsection">
1422 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
1423</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1424
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1425<div class="doc_text">
1426<p>This class provides a symbol table that the <a
1427href="#Function"><tt>Function</tt></a> and <a href="#Module">
1428<tt>Module</tt></a> classes use for naming definitions. The symbol table can
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1429provide a name for any <a href="#Value"><tt>Value</tt></a>.
1430<tt>SymbolTable</tt> is an abstract data type. It hides the data it contains
1431and provides access to it through a controlled interface.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1432
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1433<p>Note that the <tt>SymbolTable</tt> class should not be directly accessed
1434by most clients. It should only be used when iteration over the symbol table
1435names themselves are required, which is very special purpose. Note that not
1436all LLVM
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1437<a href="#Value">Value</a>s have names, and those without names (i.e. they have
1438an empty name) do not exist in the symbol table.
1439</p>
1440
1441<p>To use the <tt>SymbolTable</tt> well, you need to understand the
1442structure of the information it holds. The class contains two
1443<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
1444<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1445Thus, Values are stored in two-dimensions and accessed by <tt>Type</tt> and
1446name.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1447
1448<p>The interface of this class provides three basic types of operations:
1449<ol>
1450 <li><em>Accessors</em>. Accessors provide read-only access to information
1451 such as finding a value for a name with the
1452 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1453 <li><em>Mutators</em>. Mutators allow the user to add information to the
1454 <tt>SymbolTable</tt> with methods like
1455 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1456 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1457 of the symbol table in well defined ways, such as the method
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1458 <a href="#SymbolTable_plane_begin"><tt>plane_begin</tt></a>.</li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1459</ol>
1460
1461<h3>Accessors</h3>
1462<dl>
1463 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
1464 </dt>
1465 <dd>The <tt>lookup</tt> method searches the type plane given by the
1466 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1467 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1468
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1469 <dt><tt>bool isEmpty() const</tt>:</dt>
1470 <dd>This function returns true if both the value and types maps are
1471 empty</dd>
1472</dl>
1473
1474<h3>Mutators</h3>
1475<dl>
1476 <dt><tt>void insert(Value *Val)</tt>:</dt>
1477 <dd>This method adds the provided value to the symbol table. The Value must
1478 have both a name and a type which are extracted and used to place the value
1479 in the correct type plane under the value's name.</dd>
1480
1481 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1482 <dd> Inserts a constant or type into the symbol table with the specified
1483 name. There can be a many to one mapping between names and constants
1484 or types.</dd>
1485
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1486 <dt><tt>void remove(Value* Val)</tt>:</dt>
1487 <dd> This method removes a named value from the symbol table. The
1488 type and name of the Value are extracted from \p N and used to
1489 lookup the Value in the correct type plane. If the Value is
1490 not in the symbol table, this method silently ignores the
1491 request.</dd>
1492
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1493 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1494 <dd> Remove a constant or type with the specified name from the
1495 symbol table.</dd>
1496
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1497 <dt><tt>Value *remove(const value_iterator&amp; It)</tt>:</dt>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1498 <dd> Removes a specific value from the symbol table.
1499 Returns the removed value.</dd>
1500
1501 <dt><tt>bool strip()</tt>:</dt>
1502 <dd> This method will strip the symbol table of its names leaving
1503 the type and values. </dd>
1504
1505 <dt><tt>void clear()</tt>:</dt>
1506 <dd>Empty the symbol table completely.</dd>
1507</dl>
1508
1509<h3>Iteration</h3>
1510<p>The following functions describe three types of iterators you can obtain
1511the beginning or end of the sequence for both const and non-const. It is
1512important to keep track of the different kinds of iterators. There are
1513three idioms worth pointing out:</p>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1514
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1515<table>
1516 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1517 <tr>
1518 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1519 <td align="left"><pre><tt>
1520for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1521 PE = ST.plane_end(); PI != PE; ++PI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1522 PI-&gt;first // <i>This is the Type* of the plane</i>
1523 PI-&gt;second // <i>This is the SymbolTable::ValueMap of name/Value pairs</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1524}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1525 </tt></pre></td>
1526 </tr>
1527 <tr>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1528 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1529 <td align="left"><pre><tt>
1530for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1531 VE = ST.value_end(SomeType); VI != VE; ++VI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1532 VI-&gt;first // <i>This is the name of the Value</i>
1533 VI-&gt;second // <i>This is the Value* value associated with the name</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1534}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1535 </tt></pre></td>
1536 </tr>
1537</table>
1538
1539<p>Using the recommended iterator names and idioms will help you avoid
1540making mistakes. Of particular note, make sure that whenever you use
1541value_begin(SomeType) that you always compare the resulting iterator
1542with value_end(SomeType) not value_end(SomeOtherType) or else you
1543will loop infinitely.</p>
1544
1545<dl>
1546
1547 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1548 <dd>Get an iterator that starts at the beginning of the type planes.
1549 The iterator will iterate over the Type/ValueMap pairs in the
1550 type planes. </dd>
1551
1552 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1553 <dd>Get a const_iterator that starts at the beginning of the type
1554 planes. The iterator will iterate over the Type/ValueMap pairs
1555 in the type planes. </dd>
1556
1557 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1558 <dd>Get an iterator at the end of the type planes. This serves as
1559 the marker for end of iteration over the type planes.</dd>
1560
1561 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1562 <dd>Get a const_iterator at the end of the type planes. This serves as
1563 the marker for end of iteration over the type planes.</dd>
1564
1565 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
1566 <dd>Get an iterator that starts at the beginning of a type plane.
1567 The iterator will iterate over the name/value pairs in the type plane.
1568 Note: The type plane must already exist before using this.</dd>
1569
1570 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
1571 <dd>Get a const_iterator that starts at the beginning of a type plane.
1572 The iterator will iterate over the name/value pairs in the type plane.
1573 Note: The type plane must already exist before using this.</dd>
1574
1575 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
1576 <dd>Get an iterator to the end of a type plane. This serves as the marker
1577 for end of iteration of the type plane.
1578 Note: The type plane must already exist before using this.</dd>
1579
1580 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
1581 <dd>Get a const_iterator to the end of a type plane. This serves as the
1582 marker for end of iteration of the type plane.
1583 Note: the type plane must already exist before using this.</dd>
1584
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1585 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
1586 <dd>This method returns a plane_const_iterator for iteration over
1587 the type planes starting at a specific plane, given by \p Ty.</dd>
1588
1589 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
1590 <dd>This method returns a plane_iterator for iteration over the
1591 type planes starting at a specific plane, given by \p Ty.</dd>
1592
1593</dl>
1594</div>
1595
1596
1597
1598<!-- *********************************************************************** -->
1599<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1600 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
1601</div>
1602<!-- *********************************************************************** -->
1603
1604<div class="doc_text">
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]1605<p><tt>#include "<a href="/doxygen/Type_8h-source.html">llvm/Type.h</a>"</tt>
1606<br>doxygen info: <a href="/doxygen/classllvm_1_1Type.html">Type Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1607
1608<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1609being inspected or transformed. The core LLVM classes are defined in
1610header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1611the <tt>lib/VMCore</tt> directory.</p>
1612
1613</div>
1614
1615<!-- ======================================================================= -->
1616<div class="doc_subsection">
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]1617 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
1618</div>
1619
1620<div class="doc_text">
1621
1622 <p><tt>Type</tt> is a superclass of all type classes. Every <tt>Value</tt> has
1623 a <tt>Type</tt>. <tt>Type</tt> cannot be instantiated directly but only
1624 through its subclasses. Certain primitive types (<tt>VoidType</tt>,
1625 <tt>LabelType</tt>, <tt>FloatType</tt> and <tt>DoubleType</tt>) have hidden
1626 subclasses. They are hidden because they offer no useful functionality beyond
1627 what the <tt>Type</tt> class offers except to distinguish themselves from
1628 other subclasses of <tt>Type</tt>.</p>
1629 <p>All other types are subclasses of <tt>DerivedType</tt>. Types can be
1630 named, but this is not a requirement. There exists exactly
1631 one instance of a given shape at any one time. This allows type equality to
1632 be performed with address equality of the Type Instance. That is, given two
1633 <tt>Type*</tt> values, the types are identical if the pointers are identical.
1634 </p>
1635</div>
1636
1637<!-- _______________________________________________________________________ -->
1638<div class="doc_subsubsection">
1639 <a name="m_Value">Important Public Methods</a>
1640</div>
1641
1642<div class="doc_text">
1643
1644<ul>
Chris Lattner8f79df32007-01-15 01:55:32 +0000[diff] [blame]1645 <li><tt>bool isInteger() const</tt>: Returns true for any integer type.</li>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]1646
1647 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
1648 floating point types.</li>
1649
1650 <li><tt>bool isAbstract()</tt>: Return true if the type is abstract (contains
1651 an OpaqueType anywhere in its definition).</li>
1652
1653 <li><tt>bool isSized()</tt>: Return true if the type has known size. Things
1654 that don't have a size are abstract types, labels and void.</li>
1655
1656</ul>
1657</div>
1658
1659<!-- _______________________________________________________________________ -->
1660<div class="doc_subsubsection">
1661 <a name="m_Value">Important Derived Types</a>
1662</div>
1663<div class="doc_text">
1664<dl>
1665 <dt><tt>IntegerType</tt></dt>
1666 <dd>Subclass of DerivedType that represents integer types of any bit width.
1667 Any bit width between <tt>IntegerType::MIN_INT_BITS</tt> (1) and
1668 <tt>IntegerType::MAX_INT_BITS</tt> (~8 million) can be represented.
1669 <ul>
1670 <li><tt>static const IntegerType* get(unsigned NumBits)</tt>: get an integer
1671 type of a specific bit width.</li>
1672 <li><tt>unsigned getBitWidth() const</tt>: Get the bit width of an integer
1673 type.</li>
1674 </ul>
1675 </dd>
1676 <dt><tt>SequentialType</tt></dt>
1677 <dd>This is subclassed by ArrayType and PointerType
1678 <ul>
1679 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
1680 of the elements in the sequential type. </li>
1681 </ul>
1682 </dd>
1683 <dt><tt>ArrayType</tt></dt>
1684 <dd>This is a subclass of SequentialType and defines the interface for array
1685 types.
1686 <ul>
1687 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
1688 elements in the array. </li>
1689 </ul>
1690 </dd>
1691 <dt><tt>PointerType</tt></dt>
1692 <dd>Subclass of SequentialType for pointer types.</li>
1693 <dt><tt>PackedType</tt></dt>
1694 <dd>Subclass of SequentialType for packed (vector) types. A
1695 packed type is similar to an ArrayType but is distinguished because it is
1696 a first class type wherease ArrayType is not. Packed types are used for
1697 vector operations and are usually small vectors of of an integer or floating
1698 point type.</dd>
1699 <dt><tt>StructType</tt></dt>
1700 <dd>Subclass of DerivedTypes for struct types.</dd>
1701 <dt><tt>FunctionType</tt></dt>
1702 <dd>Subclass of DerivedTypes for function types.
1703 <ul>
1704 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
1705 function</li>
1706 <li><tt> const Type * getReturnType() const</tt>: Returns the
1707 return type of the function.</li>
1708 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
1709 the type of the ith parameter.</li>
1710 <li><tt> const unsigned getNumParams() const</tt>: Returns the
1711 number of formal parameters.</li>
1712 </ul>
1713 </dd>
1714 <dt><tt>OpaqueType</tt></dt>
1715 <dd>Sublcass of DerivedType for abstract types. This class
1716 defines no content and is used as a placeholder for some other type. Note
1717 that OpaqueType is used (temporarily) during type resolution for forward
1718 references of types. Once the referenced type is resolved, the OpaqueType
1719 is replaced with the actual type. OpaqueType can also be used for data
1720 abstraction. At link time opaque types can be resolved to actual types
1721 of the same name.</dd>
1722</dl>
1723</div>
1724
1725<!-- ======================================================================= -->
1726<div class="doc_subsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1727 <a name="Value">The <tt>Value</tt> class</a>
1728</div>
1729
1730<div>
1731
1732<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
1733<br>
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]1734doxygen info: <a href="/doxygen/classllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1735
1736<p>The <tt>Value</tt> class is the most important class in the LLVM Source
1737base. It represents a typed value that may be used (among other things) as an
1738operand to an instruction. There are many different types of <tt>Value</tt>s,
1739such as <a href="#Constant"><tt>Constant</tt></a>s,<a
1740href="#Argument"><tt>Argument</tt></a>s. Even <a
1741href="#Instruction"><tt>Instruction</tt></a>s and <a
1742href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
1743
1744<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
1745for a program. For example, an incoming argument to a function (represented
1746with an instance of the <a href="#Argument">Argument</a> class) is "used" by
1747every instruction in the function that references the argument. To keep track
1748of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
1749href="#User"><tt>User</tt></a>s that is using it (the <a
1750href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
1751graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
1752def-use information in the program, and is accessible through the <tt>use_</tt>*
1753methods, shown below.</p>
1754
1755<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
1756and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
1757method. In addition, all LLVM values can be named. The "name" of the
1758<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
1759
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1760<div class="doc_code">
1761<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1762%<b>foo</b> = add i32 1, 2
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1763</pre>
1764</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1765
1766<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
1767that the name of any value may be missing (an empty string), so names should
1768<b>ONLY</b> be used for debugging (making the source code easier to read,
1769debugging printouts), they should not be used to keep track of values or map
1770between them. For this purpose, use a <tt>std::map</tt> of pointers to the
1771<tt>Value</tt> itself instead.</p>
1772
1773<p>One important aspect of LLVM is that there is no distinction between an SSA
1774variable and the operation that produces it. Because of this, any reference to
1775the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]1776argument, for example) is represented as a direct pointer to the instance of
1777the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1778represents this value. Although this may take some getting used to, it
1779simplifies the representation and makes it easier to manipulate.</p>
1780
1781</div>
1782
1783<!-- _______________________________________________________________________ -->
1784<div class="doc_subsubsection">
1785 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
1786</div>
1787
1788<div class="doc_text">
1789
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1790<ul>
1791 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
1792use-list<br>
1793 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
1794the use-list<br>
1795 <tt>unsigned use_size()</tt> - Returns the number of users of the
1796value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1797 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1798 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
1799the use-list.<br>
1800 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
1801use-list.<br>
1802 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
1803element in the list.
1804 <p> These methods are the interface to access the def-use
1805information in LLVM. As with all other iterators in LLVM, the naming
1806conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1807 </li>
1808 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1809 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1810 </li>
1811 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1812 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1813 <tt>void setName(const std::string &amp;Name)</tt>
1814 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
1815be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1816 </li>
1817 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1818
1819 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
1820 href="#User"><tt>User</tt>s</a> of the current value to refer to
1821 "<tt>V</tt>" instead. For example, if you detect that an instruction always
1822 produces a constant value (for example through constant folding), you can
1823 replace all uses of the instruction with the constant like this:</p>
1824
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1825<div class="doc_code">
1826<pre>
1827Inst-&gt;replaceAllUsesWith(ConstVal);
1828</pre>
1829</div>
1830
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1831</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1832
1833</div>
1834
1835<!-- ======================================================================= -->
1836<div class="doc_subsection">
1837 <a name="User">The <tt>User</tt> class</a>
1838</div>
1839
1840<div class="doc_text">
1841
1842<p>
1843<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1844doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1845Superclass: <a href="#Value"><tt>Value</tt></a></p>
1846
1847<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
1848refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1849that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1850referring to. The <tt>User</tt> class itself is a subclass of
1851<tt>Value</tt>.</p>
1852
1853<p>The operands of a <tt>User</tt> point directly to the LLVM <a
1854href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1855Single Assignment (SSA) form, there can only be one definition referred to,
1856allowing this direct connection. This connection provides the use-def
1857information in LLVM.</p>
1858
1859</div>
1860
1861<!-- _______________________________________________________________________ -->
1862<div class="doc_subsubsection">
1863 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
1864</div>
1865
1866<div class="doc_text">
1867
1868<p>The <tt>User</tt> class exposes the operand list in two ways: through
1869an index access interface and through an iterator based interface.</p>
1870
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1871<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1872 <li><tt>Value *getOperand(unsigned i)</tt><br>
1873 <tt>unsigned getNumOperands()</tt>
1874 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1875convenient form for direct access.</p></li>
1876
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1877 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
1878list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1879 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
1880the operand list.<br>
1881 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1882operand list.
1883 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1884the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1885</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1886
1887</div>
1888
1889<!-- ======================================================================= -->
1890<div class="doc_subsection">
1891 <a name="Instruction">The <tt>Instruction</tt> class</a>
1892</div>
1893
1894<div class="doc_text">
1895
1896<p><tt>#include "</tt><tt><a
1897href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1898doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1899Superclasses: <a href="#User"><tt>User</tt></a>, <a
1900href="#Value"><tt>Value</tt></a></p>
1901
1902<p>The <tt>Instruction</tt> class is the common base class for all LLVM
1903instructions. It provides only a few methods, but is a very commonly used
1904class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1905opcode (instruction type) and the parent <a
1906href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1907into. To represent a specific type of instruction, one of many subclasses of
1908<tt>Instruction</tt> are used.</p>
1909
1910<p> Because the <tt>Instruction</tt> class subclasses the <a
1911href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1912way as for other <a href="#User"><tt>User</tt></a>s (with the
1913<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1914<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
1915the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
1916file contains some meta-data about the various different types of instructions
1917in LLVM. It describes the enum values that are used as opcodes (for example
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]1918<tt>Instruction::Add</tt> and <tt>Instruction::ICmp</tt>), as well as the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1919concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
1920example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]1921href="#CmpInst">CmpInst</a></tt>). Unfortunately, the use of macros in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1922this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1923<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1924
1925</div>
1926
1927<!-- _______________________________________________________________________ -->
1928<div class="doc_subsubsection">
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]1929 <a name="s_Instruction">Important Subclasses of the <tt>Instruction</tt>
1930 class</a>
1931</div>
1932<div class="doc_text">
1933 <ul>
1934 <li><tt><a name="BinaryOperator">BinaryOperator</a></tt>
1935 <p>This subclasses represents all two operand instructions whose operands
1936 must be the same type, except for the comparison instructions.</p></li>
1937 <li><tt><a name="CastInst">CastInst</a></tt>
1938 <p>This subclass is the parent of the 12 casting instructions. It provides
1939 common operations on cast instructions.</p>
1940 <li><tt><a name="CmpInst">CmpInst</a></tt>
1941 <p>This subclass respresents the two comparison instructions,
1942 <a href="LangRef.html#i_icmp">ICmpInst</a> (integer opreands), and
1943 <a href="LangRef.html#i_fcmp">FCmpInst</a> (floating point operands).</p>
1944 <li><tt><a name="TerminatorInst">TerminatorInst</a></tt>
1945 <p>This subclass is the parent of all terminator instructions (those which
1946 can terminate a block).</p>
1947 </ul>
1948 </div>
1949
1950<!-- _______________________________________________________________________ -->
1951<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1952 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
1953 class</a>
1954</div>
1955
1956<div class="doc_text">
1957
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1958<ul>
1959 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1960 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
1961this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1962 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1963 <p>Returns true if the instruction writes to memory, i.e. it is a
1964 <tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1965 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1966 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1967 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1968 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1969in all ways to the original except that the instruction has no parent
1970(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1971and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1972</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1973
1974</div>
1975
1976<!-- ======================================================================= -->
1977<div class="doc_subsection">
1978 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1979</div>
1980
1981<div class="doc_text">
1982
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1983<p><tt>#include "<a
1984href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
1985doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
1986Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1987Superclass: <a href="#Value"><tt>Value</tt></a></p>
1988
1989<p>This class represents a single entry multiple exit section of the code,
1990commonly known as a basic block by the compiler community. The
1991<tt>BasicBlock</tt> class maintains a list of <a
1992href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
1993Matching the language definition, the last element of this list of instructions
1994is always a terminator instruction (a subclass of the <a
1995href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
1996
1997<p>In addition to tracking the list of instructions that make up the block, the
1998<tt>BasicBlock</tt> class also keeps track of the <a
1999href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
2000
2001<p>Note that <tt>BasicBlock</tt>s themselves are <a
2002href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
2003like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
2004<tt>label</tt>.</p>
2005
2006</div>
2007
2008<!-- _______________________________________________________________________ -->
2009<div class="doc_subsubsection">
2010 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
2011 class</a>
2012</div>
2013
2014<div class="doc_text">
2015
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2016<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2017
2018<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2019 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2020
2021<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
2022insertion into a function. The constructor optionally takes a name for the new
2023block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
2024the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
2025automatically inserted at the end of the specified <a
2026href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
2027manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
2028
2029<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
2030<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
2031<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2032<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2033STL-style functions for accessing the instruction list.
2034
2035<p>These methods and typedefs are forwarding functions that have the same
2036semantics as the standard library methods of the same names. These methods
2037expose the underlying instruction list of a basic block in a way that is easy to
2038manipulate. To get the full complement of container operations (including
2039operations to update the list), you must use the <tt>getInstList()</tt>
2040method.</p></li>
2041
2042<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
2043
2044<p>This method is used to get access to the underlying container that actually
2045holds the Instructions. This method must be used when there isn't a forwarding
2046function in the <tt>BasicBlock</tt> class for the operation that you would like
2047to perform. Because there are no forwarding functions for "updating"
2048operations, you need to use this if you want to update the contents of a
2049<tt>BasicBlock</tt>.</p></li>
2050
2051<li><tt><a href="#Function">Function</a> *getParent()</tt>
2052
2053<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
2054embedded into, or a null pointer if it is homeless.</p></li>
2055
2056<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
2057
2058<p> Returns a pointer to the terminator instruction that appears at the end of
2059the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
2060instruction in the block is not a terminator, then a null pointer is
2061returned.</p></li>
2062
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2063</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2064
2065</div>
2066
2067<!-- ======================================================================= -->
2068<div class="doc_subsection">
2069 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
2070</div>
2071
2072<div class="doc_text">
2073
2074<p><tt>#include "<a
2075href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2076doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
2077Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2078Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
2079<a href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2080
2081<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
2082href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
2083visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
2084Because they are visible at global scope, they are also subject to linking with
2085other globals defined in different translation units. To control the linking
2086process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
2087<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2088defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2089
2090<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
2091<tt>static</tt> in C), it is not visible to code outside the current translation
2092unit, and does not participate in linking. If it has external linkage, it is
2093visible to external code, and does participate in linking. In addition to
2094linkage information, <tt>GlobalValue</tt>s keep track of which <a
2095href="#Module"><tt>Module</tt></a> they are currently part of.</p>
2096
2097<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
2098by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
2099global is always a pointer to its contents. It is important to remember this
2100when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
2101be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
2102subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2103i32]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2104the address of the first element of this array and the value of the
2105<tt>GlobalVariable</tt> are the same, they have different types. The
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2106<tt>GlobalVariable</tt>'s type is <tt>[24 x i32]</tt>. The first element's type
2107is <tt>i32.</tt> Because of this, accessing a global value requires you to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2108dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
2109can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
2110Language Reference Manual</a>.</p>
2111
2112</div>
2113
2114<!-- _______________________________________________________________________ -->
2115<div class="doc_subsubsection">
2116 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
2117 class</a>
2118</div>
2119
2120<div class="doc_text">
2121
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2122<ul>
2123 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2124 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2125 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
2126 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
2127 <p> </p>
2128 </li>
2129 <li><tt><a href="#Module">Module</a> *getParent()</tt>
2130 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2131GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2132</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2133
2134</div>
2135
2136<!-- ======================================================================= -->
2137<div class="doc_subsection">
2138 <a name="Function">The <tt>Function</tt> class</a>
2139</div>
2140
2141<div class="doc_text">
2142
2143<p><tt>#include "<a
2144href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2145info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2146Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2147<a href="#Constant"><tt>Constant</tt></a>,
2148<a href="#User"><tt>User</tt></a>,
2149<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2150
2151<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
2152actually one of the more complex classes in the LLVM heirarchy because it must
2153keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2154of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
2155<a href="#Argument"><tt>Argument</tt></a>s, and a
2156<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2157
2158<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
2159commonly used part of <tt>Function</tt> objects. The list imposes an implicit
2160ordering of the blocks in the function, which indicate how the code will be
2161layed out by the backend. Additionally, the first <a
2162href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
2163<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
2164block. There are no implicit exit nodes, and in fact there may be multiple exit
2165nodes from a single <tt>Function</tt>. If the <a
2166href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
2167the <tt>Function</tt> is actually a function declaration: the actual body of the
2168function hasn't been linked in yet.</p>
2169
2170<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
2171<tt>Function</tt> class also keeps track of the list of formal <a
2172href="#Argument"><tt>Argument</tt></a>s that the function receives. This
2173container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
2174nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
2175the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
2176
2177<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
2178LLVM feature that is only used when you have to look up a value by name. Aside
2179from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
2180internally to make sure that there are not conflicts between the names of <a
2181href="#Instruction"><tt>Instruction</tt></a>s, <a
2182href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
2183href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
2184
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2185<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
2186and therefore also a <a href="#Constant">Constant</a>. The value of the function
2187is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2188</div>
2189
2190<!-- _______________________________________________________________________ -->
2191<div class="doc_subsubsection">
2192 <a name="m_Function">Important Public Members of the <tt>Function</tt>
2193 class</a>
2194</div>
2195
2196<div class="doc_text">
2197
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2198<ul>
2199 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2200 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2201
2202 <p>Constructor used when you need to create new <tt>Function</tt>s to add
2203 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2204 create and what type of linkage the function should have. The <a
2205 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2206 specifies the formal arguments and return value for the function. The same
2207 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
2208 create multiple functions. The <tt>Parent</tt> argument specifies the Module
2209 in which the function is defined. If this argument is provided, the function
2210 will automatically be inserted into that module's list of
2211 functions.</p></li>
2212
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2213 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2214
2215 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
2216 function is "external", it does not have a body, and thus must be resolved
2217 by linking with a function defined in a different translation unit.</p></li>
2218
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2219 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2220 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2221
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2222 <tt>begin()</tt>, <tt>end()</tt>
2223 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2224
2225 <p>These are forwarding methods that make it easy to access the contents of
2226 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
2227 list.</p></li>
2228
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2229 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2230
2231 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
2232 is necessary to use when you need to update the list or perform a complex
2233 action that doesn't have a forwarding method.</p></li>
2234
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2235 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2236iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2237 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2238
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2239 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2240 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2241
2242 <p>These are forwarding methods that make it easy to access the contents of
2243 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
2244 list.</p></li>
2245
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2246 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2247
2248 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
2249 necessary to use when you need to update the list or perform a complex
2250 action that doesn't have a forwarding method.</p></li>
2251
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2252 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2253
2254 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
2255 function. Because the entry block for the function is always the first
2256 block, this returns the first block of the <tt>Function</tt>.</p></li>
2257
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2258 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
2259 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2260
2261 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
2262 <tt>Function</tt> and returns the return type of the function, or the <a
2263 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
2264 function.</p></li>
2265
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2266 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2267
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2268 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2269 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2270</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2271
2272</div>
2273
2274<!-- ======================================================================= -->
2275<div class="doc_subsection">
2276 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
2277</div>
2278
2279<div class="doc_text">
2280
2281<p><tt>#include "<a
2282href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
2283<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2284doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2285 Class</a><br>
2286Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2287<a href="#Constant"><tt>Constant</tt></a>,
2288<a href="#User"><tt>User</tt></a>,
2289<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2290
2291<p>Global variables are represented with the (suprise suprise)
2292<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
2293subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
2294always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2295"name" refers to their constant address). See
2296<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
2297variables may have an initial value (which must be a
2298<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
2299they may be marked as "constant" themselves (indicating that their contents
2300never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2301</div>
2302
2303<!-- _______________________________________________________________________ -->
2304<div class="doc_subsubsection">
2305 <a name="m_GlobalVariable">Important Public Members of the
2306 <tt>GlobalVariable</tt> class</a>
2307</div>
2308
2309<div class="doc_text">
2310
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2311<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2312 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
2313 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
2314 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
2315
2316 <p>Create a new global variable of the specified type. If
2317 <tt>isConstant</tt> is true then the global variable will be marked as
2318 unchanging for the program. The Linkage parameter specifies the type of
2319 linkage (internal, external, weak, linkonce, appending) for the variable. If
2320 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
2321 the resultant global variable will have internal linkage. AppendingLinkage
2322 concatenates together all instances (in different translation units) of the
2323 variable into a single variable but is only applicable to arrays. &nbsp;See
2324 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
2325 further details on linkage types. Optionally an initializer, a name, and the
2326 module to put the variable into may be specified for the global variable as
2327 well.</p></li>
2328
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2329 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2330
2331 <p>Returns true if this is a global variable that is known not to
2332 be modified at runtime.</p></li>
2333
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2334 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2335
2336 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
2337
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2338 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2339
2340 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
2341 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2342</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2343
2344</div>
2345
2346<!-- ======================================================================= -->
2347<div class="doc_subsection">
2348 <a name="Module">The <tt>Module</tt> class</a>
2349</div>
2350
2351<div class="doc_text">
2352
2353<p><tt>#include "<a
2354href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2355<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2356
2357<p>The <tt>Module</tt> class represents the top level structure present in LLVM
2358programs. An LLVM module is effectively either a translation unit of the
2359original program or a combination of several translation units merged by the
2360linker. The <tt>Module</tt> class keeps track of a list of <a
2361href="#Function"><tt>Function</tt></a>s, a list of <a
2362href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
2363href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
2364helpful member functions that try to make common operations easy.</p>
2365
2366</div>
2367
2368<!-- _______________________________________________________________________ -->
2369<div class="doc_subsubsection">
2370 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
2371</div>
2372
2373<div class="doc_text">
2374
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2375<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2376 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2377</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2378
2379<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
2380provide a name for it (probably based on the name of the translation unit).</p>
2381
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2382<ul>
2383 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]2384 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2385
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2386 <tt>begin()</tt>, <tt>end()</tt>
2387 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2388
2389 <p>These are forwarding methods that make it easy to access the contents of
2390 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
2391 list.</p></li>
2392
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2393 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2394
2395 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
2396 necessary to use when you need to update the list or perform a complex
2397 action that doesn't have a forwarding method.</p>
2398
2399 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2400</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2401
2402<hr>
2403
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2404<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2405 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2406
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2407 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2408
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2409 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2410 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2411
2412 <p> These are forwarding methods that make it easy to access the contents of
2413 a <tt>Module</tt> object's <a
2414 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
2415
2416 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
2417
2418 <p>Returns the list of <a
2419 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2420 use when you need to update the list or perform a complex action that
2421 doesn't have a forwarding method.</p>
2422
2423 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2424</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2425
2426<hr>
2427
2428<ul>
2429 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2430
2431 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2432 for this <tt>Module</tt>.</p>
2433
2434 <p><!-- Convenience methods --></p></li>
2435</ul>
2436
2437<hr>
2438
2439<ul>
2440 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2441 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2442
2443 <p>Look up the specified function in the <tt>Module</tt> <a
2444 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2445 <tt>null</tt>.</p></li>
2446
2447 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2448 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2449
2450 <p>Look up the specified function in the <tt>Module</tt> <a
2451 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2452 external declaration for the function and return it.</p></li>
2453
2454 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2455
2456 <p>If there is at least one entry in the <a
2457 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2458 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2459 string.</p></li>
2460
2461 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
2462 href="#Type">Type</a> *Ty)</tt>
2463
2464 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2465 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2466 name, true is returned and the <a
2467 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2468</ul>
2469
2470</div>
2471
2472<!-- ======================================================================= -->
2473<div class="doc_subsection">
2474 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2475</div>
2476
2477<div class="doc_text">
2478
2479<p>Constant represents a base class for different types of constants. It
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2480is subclassed by ConstantInt, ConstantArray, etc. for representing
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame]2481the various types of Constants.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2482
2483</div>
2484
2485<!-- _______________________________________________________________________ -->
2486<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2487 <a name="m_Constant">Important Public Methods</a>
2488</div>
2489<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2490</div>
2491
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2492<!-- _______________________________________________________________________ -->
2493<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2494<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2495<ul>
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2496 <li>ConstantInt : This subclass of Constant represents an integer constant of
2497 any width, including boolean (1 bit integer).
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2498 <ul>
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame]2499 <li><tt>int64_t getSExtValue() const</tt>: Returns the underlying value of
2500 this constant as a sign extended signed integer value.</li>
2501 <li><tt>uint64_t getZExtValue() const</tt>: Returns the underlying value
2502 of this constant as a zero extended unsigned integer value.</li>
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2503 <li><tt>static ConstantInt* get(const Type *Ty, uint64_t Val)</tt>:
2504 Returns the ConstantInt object that represents the value provided by
2505 <tt>Val</tt> for integer type <tt>Ty</tt>.</li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2506 </ul>
2507 </li>
2508 <li>ConstantFP : This class represents a floating point constant.
2509 <ul>
2510 <li><tt>double getValue() const</tt>: Returns the underlying value of
2511 this constant. </li>
2512 </ul>
2513 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2514 <ul>
2515 <li><tt>bool getValue() const</tt>: Returns the underlying value of this
2516 constant. </li>
2517 </ul>
2518 </li>
2519 <li>ConstantArray : This represents a constant array.
2520 <ul>
2521 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2522 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2523 </ul>
2524 </li>
2525 <li>ConstantStruct : This represents a constant struct.
2526 <ul>
2527 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2528 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2529 </ul>
2530 </li>
2531 <li>GlobalValue : This represents either a global variable or a function. In
2532 either case, the value is a constant fixed address (after linking).
2533 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2534</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2535</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2536<!-- ======================================================================= -->
2537<div class="doc_subsection">
2538 <a name="Argument">The <tt>Argument</tt> class</a>
2539</div>
2540
2541<div class="doc_text">
2542
2543<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2544arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2545arguments. An argument has a pointer to the parent Function.</p>
2546
2547</div>
2548
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2549<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2550<hr>
2551<address>
2552 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
2553 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
2554 <a href="http://validator.w3.org/check/referer"><img
2555 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
2556
2557 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2558 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2559 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2560 Last modified: $Date$
2561</address>
2562
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2563</body>
2564</html>