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4<head>
5 <title>LLVM Programmer's Manual</title>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]6 <link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]7</head>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]8<body>
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>
38 <li><a href="#Statistic">The <tt>Statistic</tt> template &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 Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]102 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]103 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]104 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]105 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]106 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
107 <ul>
108 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
109 </ul>
110 </li>
111 <li><a href="#Module">The <tt>Module</tt> class</a></li>
112 <li><a href="#Constant">The <tt>Constant</tt> class</a>
113 <ul>
114 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
115 <ul>
116 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
117 <li><a href="#Function">The <tt>Function</tt> class</a></li>
118 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
119 </ul>
120 </li>
121 </ul>
122 </li>
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]123 </ul>
124 </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]125 <li><a href="#Type">The <tt>Type</tt> class</a> </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 Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]306 <i>// Otherwise, it must be an instruction...</i>
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)) {
332 // ...
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>
398DEBUG(std::cerr &lt;&lt; "I am here!\n");
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
407&lt;no output&gt;
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>
443DEBUG(std::cerr &lt;&lt; "No debug type\n");
444#undef DEBUG_TYPE
445#define DEBUG_TYPE "foo"
446DEBUG(std::cerr &lt;&lt; "'foo' debug type\n");
447#undef DEBUG_TYPE
448#define DEBUG_TYPE "bar"
449DEBUG(std::cerr &lt;&lt; "'bar' debug type\n");
450#undef DEBUG_TYPE
451#define DEBUG_TYPE ""
452DEBUG(std::cerr &lt;&lt; "No debug type (2)\n");
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
461&lt;no output&gt;
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">
488 <a name="Statistic">The <tt>Statistic</tt> template &amp; <tt>-stats</tt>
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
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]496provides a template named <tt>Statistic</tt> that is used as a unified way to
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
504for big programs. Using the <tt>Statistic</tt> template makes it very easy to
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>
516static Statistic&lt;&gt; NumXForms("mypassname", "The # of times I did stuff");
517</pre>
518</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]519
520 <p>The <tt>Statistic</tt> template can emulate just about any data-type,
521 but if you do not specify a template argument, it defaults to acting like
522 an unsigned int counter (this is usually what you want).</p></li>
523
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]524 <li><p>Whenever you make a transformation, bump the counter:</p>
525
526<div class="doc_code">
527<pre>
528++NumXForms; // I did stuff!
529</pre>
530</div>
531
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]532 </li>
533 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]534
535 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
536 statistics gathered, use the '<tt>-stats</tt>' option:</p>
537
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]538<div class="doc_code">
539<pre>
540$ opt -stats -mypassname &lt; program.bc &gt; /dev/null
541... statistic output ...
542</pre>
543</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]544
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]545 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
546suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]547
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]548<div class="doc_code">
549<pre>
550 7646 bytecodewriter - Number of normal instructions
551 725 bytecodewriter - Number of oversized instructions
552 129996 bytecodewriter - Number of bytecode bytes written
553 2817 raise - Number of insts DCEd or constprop'd
554 3213 raise - Number of cast-of-self removed
555 5046 raise - Number of expression trees converted
556 75 raise - Number of other getelementptr's formed
557 138 raise - Number of load/store peepholes
558 42 deadtypeelim - Number of unused typenames removed from symtab
559 392 funcresolve - Number of varargs functions resolved
560 27 globaldce - Number of global variables removed
561 2 adce - Number of basic blocks removed
562 134 cee - Number of branches revectored
563 49 cee - Number of setcc instruction eliminated
564 532 gcse - Number of loads removed
565 2919 gcse - Number of instructions removed
566 86 indvars - Number of canonical indvars added
567 87 indvars - Number of aux indvars removed
568 25 instcombine - Number of dead inst eliminate
569 434 instcombine - Number of insts combined
570 248 licm - Number of load insts hoisted
571 1298 licm - Number of insts hoisted to a loop pre-header
572 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
573 75 mem2reg - Number of alloca's promoted
574 1444 cfgsimplify - Number of blocks simplified
575</pre>
576</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]577
578<p>Obviously, with so many optimizations, having a unified framework for this
579stuff is very nice. Making your pass fit well into the framework makes it more
580maintainable and useful.</p>
581
582</div>
583
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]584<!-- ======================================================================= -->
585<div class="doc_subsection">
586 <a name="ViewGraph">Viewing graphs while debugging code</a>
587</div>
588
589<div class="doc_text">
590
591<p>Several of the important data structures in LLVM are graphs: for example
592CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
593LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
594<a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
595DAGs</a>. In many cases, while debugging various parts of the compiler, it is
596nice to instantly visualize these graphs.</p>
597
598<p>LLVM provides several callbacks that are available in a debug build to do
599exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
600the current LLVM tool will pop up a window containing the CFG for the function
601where each basic block is a node in the graph, and each node contains the
602instructions in the block. Similarly, there also exists
603<tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
604<tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
605and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]606you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]607up a window. Alternatively, you can sprinkle calls to these functions in your
608code in places you want to debug.</p>
609
610<p>Getting this to work requires a small amount of configuration. On Unix
611systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
612toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
613Mac OS/X, download and install the Mac OS/X <a
614href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
615<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
616it) to your path. Once in your system and path are set up, rerun the LLVM
617configure script and rebuild LLVM to enable this functionality.</p>
618
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]619<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
620<i>interesting</i> nodes in large complex graphs. From gdb, if you
621<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
622next <tt>call DAG.viewGraph()</tt> would hilight the node in the
623specified color (choices of colors can be found at <a
624href="http://www.graphviz.org/doc/info/colors.html">Colors<a>.) More
625complex node attributes can be provided with <tt>call
626DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
627found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
628Attributes</a>.) If you want to restart and clear all the current graph
629attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
630
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]631</div>
632
633
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]634<!-- *********************************************************************** -->
635<div class="doc_section">
636 <a name="common">Helpful Hints for Common Operations</a>
637</div>
638<!-- *********************************************************************** -->
639
640<div class="doc_text">
641
642<p>This section describes how to perform some very simple transformations of
643LLVM code. This is meant to give examples of common idioms used, showing the
644practical side of LLVM transformations. <p> Because this is a "how-to" section,
645you should also read about the main classes that you will be working with. The
646<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
647and descriptions of the main classes that you should know about.</p>
648
649</div>
650
651<!-- NOTE: this section should be heavy on example code -->
652<!-- ======================================================================= -->
653<div class="doc_subsection">
654 <a name="inspection">Basic Inspection and Traversal Routines</a>
655</div>
656
657<div class="doc_text">
658
659<p>The LLVM compiler infrastructure have many different data structures that may
660be traversed. Following the example of the C++ standard template library, the
661techniques used to traverse these various data structures are all basically the
662same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
663method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
664function returns an iterator pointing to one past the last valid element of the
665sequence, and there is some <tt>XXXiterator</tt> data type that is common
666between the two operations.</p>
667
668<p>Because the pattern for iteration is common across many different aspects of
669the program representation, the standard template library algorithms may be used
670on them, and it is easier to remember how to iterate. First we show a few common
671examples of the data structures that need to be traversed. Other data
672structures are traversed in very similar ways.</p>
673
674</div>
675
676<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]677<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]678 <a name="iterate_function">Iterating over the </a><a
679 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
680 href="#Function"><tt>Function</tt></a>
681</div>
682
683<div class="doc_text">
684
685<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
686transform in some way; in particular, you'd like to manipulate its
687<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
688the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
689an example that prints the name of a <tt>BasicBlock</tt> and the number of
690<tt>Instruction</tt>s it contains:</p>
691
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]692<div class="doc_code">
693<pre>
694// func is a pointer to a Function instance
695for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i) {
696 // print out the name of the basic block if it has one, and then the
697 // number of instructions that it contains
698 std::cerr &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has "
699 &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";
700}
701</pre>
702</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]703
704<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]705invoking member functions of the <tt>Instruction</tt> class. This is
706because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]707classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]708exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
709
710</div>
711
712<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]713<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]714 <a name="iterate_basicblock">Iterating over the </a><a
715 href="#Instruction"><tt>Instruction</tt></a>s in a <a
716 href="#BasicBlock"><tt>BasicBlock</tt></a>
717</div>
718
719<div class="doc_text">
720
721<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
722easy to iterate over the individual instructions that make up
723<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
724a <tt>BasicBlock</tt>:</p>
725
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]726<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]727<pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]728// blk is a pointer to a BasicBlock instance
729for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
730 // the next statement works since operator&lt;&lt;(ostream&amp;,...)
731 // is overloaded for Instruction&amp;
732 std::cerr &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]733</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]734</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]735
736<p>However, this isn't really the best way to print out the contents of a
737<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
738anything you'll care about, you could have just invoked the print routine on the
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]739basic block itself: <tt>std::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]740
741</div>
742
743<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]744<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]745 <a name="iterate_institer">Iterating over the </a><a
746 href="#Instruction"><tt>Instruction</tt></a>s in a <a
747 href="#Function"><tt>Function</tt></a>
748</div>
749
750<div class="doc_text">
751
752<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
753<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
754<tt>InstIterator</tt> should be used instead. You'll need to include <a
755href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
756and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]757small 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]758
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]759<div class="doc_code">
760<pre>
761#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
762
763// Suppose F is a ptr to a function
764for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
765 std::cerr &lt;&lt; *i &lt;&lt; "\n";
766</pre>
767</div>
768
769<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]770worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]771initialize a worklist to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]772F, all you would need to do is something like:</p>
773
774<div class="doc_code">
775<pre>
776std::set&lt;Instruction*&gt; worklist;
777worklist.insert(inst_begin(F), inst_end(F));
778</pre>
779</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]780
781<p>The STL set <tt>worklist</tt> would now contain all instructions in the
782<tt>Function</tt> pointed to by F.</p>
783
784</div>
785
786<!-- _______________________________________________________________________ -->
787<div class="doc_subsubsection">
788 <a name="iterate_convert">Turning an iterator into a class pointer (and
789 vice-versa)</a>
790</div>
791
792<div class="doc_text">
793
794<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]795instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]796a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]797Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]798is a <tt>BasicBlock::const_iterator</tt>:</p>
799
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]800<div class="doc_code">
801<pre>
802Instruction&amp; inst = *i; // grab reference to instruction reference
803Instruction* pinst = &amp;*i; // grab pointer to instruction reference
804const Instruction&amp; inst = *j;
805</pre>
806</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]807
808<p>However, the iterators you'll be working with in the LLVM framework are
809special: they will automatically convert to a ptr-to-instance type whenever they
810need to. Instead of dereferencing the iterator and then taking the address of
811the result, you can simply assign the iterator to the proper pointer type and
812you get the dereference and address-of operation as a result of the assignment
813(behind the scenes, this is a result of overloading casting mechanisms). Thus
814the last line of the last example,</p>
815
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]816<div class="doc_code">
817<pre>
818Instruction* pinst = &amp;*i;
819</pre>
820</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]821
822<p>is semantically equivalent to</p>
823
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]824<div class="doc_code">
825<pre>
826Instruction* pinst = i;
827</pre>
828</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]829
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]830<p>It's also possible to turn a class pointer into the corresponding iterator,
831and this is a constant time operation (very efficient). The following code
832snippet illustrates use of the conversion constructors provided by LLVM
833iterators. By using these, you can explicitly grab the iterator of something
834without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]835
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]836<div class="doc_code">
837<pre>
838void printNextInstruction(Instruction* inst) {
839 BasicBlock::iterator it(inst);
840 ++it; // after this line, it refers to the instruction after *inst.
841 if (it != inst-&gt;getParent()-&gt;end()) std::cerr &lt;&lt; *it &lt;&lt; "\n";
842}
843</pre>
844</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]845
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]846</div>
847
848<!--_______________________________________________________________________-->
849<div class="doc_subsubsection">
850 <a name="iterate_complex">Finding call sites: a slightly more complex
851 example</a>
852</div>
853
854<div class="doc_text">
855
856<p>Say that you're writing a FunctionPass and would like to count all the
857locations in the entire module (that is, across every <tt>Function</tt>) where a
858certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
859learn 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]860much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]861you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
862is what we want to do:</p>
863
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]864<div class="doc_code">
865<pre>
866initialize callCounter to zero
867for each Function f in the Module
868 for each BasicBlock b in f
869 for each Instruction i in b
870 if (i is a CallInst and calls the given function)
871 increment callCounter
872</pre>
873</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]874
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]875<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]876<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]877override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]878
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]879<div class="doc_code">
880<pre>
881Function* targetFunc = ...;
882
883class OurFunctionPass : public FunctionPass {
884 public:
885 OurFunctionPass(): callCounter(0) { }
886
887 virtual runOnFunction(Function&amp; F) {
888 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
889 for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
890 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
891 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
892 // we know we've encountered a call instruction, so we
893 // need to determine if it's a call to the
894 // function pointed to by m_func or not.
895
896 if (callInst-&gt;getCalledFunction() == targetFunc)
897 ++callCounter;
898 }
899 }
900 }
901
902
903 private:
904 unsigned callCounter;
905};
906</pre>
907</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]908
909</div>
910
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]911<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]912<div class="doc_subsubsection">
913 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
914</div>
915
916<div class="doc_text">
917
918<p>You may have noticed that the previous example was a bit oversimplified in
919that it did not deal with call sites generated by 'invoke' instructions. In
920this, and in other situations, you may find that you want to treat
921<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
922most-specific common base class is <tt>Instruction</tt>, which includes lots of
923less closely-related things. For these cases, LLVM provides a handy wrapper
924class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]925href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]926It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
927methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]928<tt>InvokeInst</tt>s.</p>
929
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]930<p>This class has "value semantics": it should be passed by value, not by
931reference and it should not be dynamically allocated or deallocated using
932<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
933assignable and constructable, with costs equivalents to that of a bare pointer.
934If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]935
936</div>
937
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]938<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]939<div class="doc_subsubsection">
940 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
941</div>
942
943<div class="doc_text">
944
945<p>Frequently, we might have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]946href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
947determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
948<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
949For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
950particular function <tt>foo</tt>. Finding all of the instructions that
951<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
952of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]953
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]954<div class="doc_code">
955<pre>
956Function* F = ...;
957
958for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i) {
959 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
960 std::cerr &lt;&lt; "F is used in instruction:\n";
961 std::cerr &lt;&lt; *Inst &lt;&lt; "\n";
962 }
963}
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;
981 ...
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
1078pb-&gt;getInstList().insert(pi, newInst); // inserts newInst before pi in pb
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
1093pb-&gt;getInstList().push_back(newInst); // appends newInst to pb
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
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1228doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
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
1281opaque type as part of its type graph (for example "<tt>{ opaque, int }</tt>").
1282Third, a concrete type is a type that is not an abstract type (e.g. "<tt>[ int,
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>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1303%mylist = type { %mylist*, int }
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 Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1313//<i> Create the initial outer struct.</i>
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
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1320//<i> At this point, NewSTy = "{ opaque*, int }". Tell VMCore that</i>
1321//<i> the struct and the opaque type are actually the same.</i>
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>
1325// <i>kept up-to-date.</i>
1326NewSTy = cast&lt;StructType&gt;(StructTy.get());
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1327
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1328// <i>Add a name for the type to the module symbol table (optional).</i>
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.
1360Additionally, if there is an "{ \2*, int}" type already created in the system,
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>
1414abstract</i> types. Concrete types (those that do not include an opaque objects
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1415somewhere) can never be refined.
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
1429provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
1430href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
1431type. It hides the data it contains and provides access to it through a
1432controlled interface.</p>
1433
1434<p>Note that the symbol table class is should not be directly accessed by most
1435clients. It should only be used when iteration over the symbol table names
1436themselves are required, which is very special purpose. Note that not all LLVM
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>.
1445The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
1446are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
1447however, are stored in a single dimension and accessed only by name.</p>
1448
1449<p>The interface of this class provides three basic types of operations:
1450<ol>
1451 <li><em>Accessors</em>. Accessors provide read-only access to information
1452 such as finding a value for a name with the
1453 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1454 <li><em>Mutators</em>. Mutators allow the user to add information to the
1455 <tt>SymbolTable</tt> with methods like
1456 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1457 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1458 of the symbol table in well defined ways, such as the method
1459 <a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
1460</ol>
1461
1462<h3>Accessors</h3>
1463<dl>
1464 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
1465 </dt>
1466 <dd>The <tt>lookup</tt> method searches the type plane given by the
1467 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1468 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1469
1470 <dt><tt>Type* lookupType( const std::string&amp; name) const</tt>:</dt>
1471 <dd>The <tt>lookupType</tt> method searches through the types for a
1472 <tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
1473 is not found, null is returned.</dd>
1474
1475 <dt><tt>bool hasTypes() const</tt>:</dt>
1476 <dd>This function returns true if an entry has been made into the type
1477 map.</dd>
1478
1479 <dt><tt>bool isEmpty() const</tt>:</dt>
1480 <dd>This function returns true if both the value and types maps are
1481 empty</dd>
1482</dl>
1483
1484<h3>Mutators</h3>
1485<dl>
1486 <dt><tt>void insert(Value *Val)</tt>:</dt>
1487 <dd>This method adds the provided value to the symbol table. The Value must
1488 have both a name and a type which are extracted and used to place the value
1489 in the correct type plane under the value's name.</dd>
1490
1491 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1492 <dd> Inserts a constant or type into the symbol table with the specified
1493 name. There can be a many to one mapping between names and constants
1494 or types.</dd>
1495
1496 <dt><tt>void insert(const std::string&amp; Name, Type *Typ)</tt>:</dt>
1497 <dd> Inserts a type into the symbol table with the specified name. There
1498 can be a many-to-one mapping between names and types. This method
1499 allows a type with an existing entry in the symbol table to get
1500 a new name.</dd>
1501
1502 <dt><tt>void remove(Value* Val)</tt>:</dt>
1503 <dd> This method removes a named value from the symbol table. The
1504 type and name of the Value are extracted from \p N and used to
1505 lookup the Value in the correct type plane. If the Value is
1506 not in the symbol table, this method silently ignores the
1507 request.</dd>
1508
1509 <dt><tt>void remove(Type* Typ)</tt>:</dt>
1510 <dd> This method removes a named type from the symbol table. The
1511 name of the type is extracted from \P T and used to look up
1512 the Type in the type map. If the Type is not in the symbol
1513 table, this method silently ignores the request.</dd>
1514
1515 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1516 <dd> Remove a constant or type with the specified name from the
1517 symbol table.</dd>
1518
1519 <dt><tt>Type* remove(const std::string&amp; Name, Type* T)</tt>:</dt>
1520 <dd> Remove a type with the specified name from the symbol table.
1521 Returns the removed Type.</dd>
1522
1523 <dt><tt>Value *value_remove(const value_iterator&amp; It)</tt>:</dt>
1524 <dd> Removes a specific value from the symbol table.
1525 Returns the removed value.</dd>
1526
1527 <dt><tt>bool strip()</tt>:</dt>
1528 <dd> This method will strip the symbol table of its names leaving
1529 the type and values. </dd>
1530
1531 <dt><tt>void clear()</tt>:</dt>
1532 <dd>Empty the symbol table completely.</dd>
1533</dl>
1534
1535<h3>Iteration</h3>
1536<p>The following functions describe three types of iterators you can obtain
1537the beginning or end of the sequence for both const and non-const. It is
1538important to keep track of the different kinds of iterators. There are
1539three idioms worth pointing out:</p>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1540
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1541<table>
1542 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1543 <tr>
1544 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1545 <td align="left"><pre><tt>
1546for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1547 PE = ST.plane_end(); PI != PE; ++PI ) {
1548 PI-&gt;first // This is the Type* of the plane
1549 PI-&gt;second // This is the SymbolTable::ValueMap of name/Value pairs
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1550}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1551 </tt></pre></td>
1552 </tr>
1553 <tr>
1554 <td align="left">All name/Type Pairs</td><td>TI</td>
1555 <td align="left"><pre><tt>
1556for (SymbolTable::type_const_iterator TI = ST.type_begin(),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1557 TE = ST.type_end(); TI != TE; ++TI ) {
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1558 TI-&gt;first // This is the name of the type
1559 TI-&gt;second // This is the Type* value associated with the name
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1560}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1561 </tt></pre></td>
1562 </tr>
1563 <tr>
1564 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1565 <td align="left"><pre><tt>
1566for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1567 VE = ST.value_end(SomeType); VI != VE; ++VI ) {
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1568 VI-&gt;first // This is the name of the Value
1569 VI-&gt;second // This is the Value* value associated with the name
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1570}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1571 </tt></pre></td>
1572 </tr>
1573</table>
1574
1575<p>Using the recommended iterator names and idioms will help you avoid
1576making mistakes. Of particular note, make sure that whenever you use
1577value_begin(SomeType) that you always compare the resulting iterator
1578with value_end(SomeType) not value_end(SomeOtherType) or else you
1579will loop infinitely.</p>
1580
1581<dl>
1582
1583 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1584 <dd>Get an iterator that starts at the beginning of the type planes.
1585 The iterator will iterate over the Type/ValueMap pairs in the
1586 type planes. </dd>
1587
1588 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1589 <dd>Get a const_iterator that starts at the beginning of the type
1590 planes. The iterator will iterate over the Type/ValueMap pairs
1591 in the type planes. </dd>
1592
1593 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1594 <dd>Get an iterator at the end of the type planes. This serves as
1595 the marker for end of iteration over the type planes.</dd>
1596
1597 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1598 <dd>Get a const_iterator at the end of the type planes. This serves as
1599 the marker for end of iteration over the type planes.</dd>
1600
1601 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
1602 <dd>Get an iterator that starts at the beginning of a type plane.
1603 The iterator will iterate over the name/value pairs in the type plane.
1604 Note: The type plane must already exist before using this.</dd>
1605
1606 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
1607 <dd>Get a const_iterator that starts at the beginning of a type plane.
1608 The iterator will iterate over the name/value pairs in the type plane.
1609 Note: The type plane must already exist before using this.</dd>
1610
1611 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
1612 <dd>Get an iterator to the end of a type plane. This serves as the marker
1613 for end of iteration of the type plane.
1614 Note: The type plane must already exist before using this.</dd>
1615
1616 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
1617 <dd>Get a const_iterator to the end of a type plane. This serves as the
1618 marker for end of iteration of the type plane.
1619 Note: the type plane must already exist before using this.</dd>
1620
1621 <dt><tt>type_iterator type_begin()</tt>:</dt>
1622 <dd>Get an iterator to the start of the name/Type map.</dd>
1623
1624 <dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
1625 <dd> Get a const_iterator to the start of the name/Type map.</dd>
1626
1627 <dt><tt>type_iterator type_end()</tt>:</dt>
1628 <dd>Get an iterator to the end of the name/Type map. This serves as the
1629 marker for end of iteration of the types.</dd>
1630
1631 <dt><tt>type_const_iterator type_end() const</tt>:</dt>
1632 <dd>Get a const-iterator to the end of the name/Type map. This serves
1633 as the marker for end of iteration of the types.</dd>
1634
1635 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
1636 <dd>This method returns a plane_const_iterator for iteration over
1637 the type planes starting at a specific plane, given by \p Ty.</dd>
1638
1639 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
1640 <dd>This method returns a plane_iterator for iteration over the
1641 type planes starting at a specific plane, given by \p Ty.</dd>
1642
1643</dl>
1644</div>
1645
1646
1647
1648<!-- *********************************************************************** -->
1649<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1650 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
1651</div>
1652<!-- *********************************************************************** -->
1653
1654<div class="doc_text">
1655
1656<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1657being inspected or transformed. The core LLVM classes are defined in
1658header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1659the <tt>lib/VMCore</tt> directory.</p>
1660
1661</div>
1662
1663<!-- ======================================================================= -->
1664<div class="doc_subsection">
1665 <a name="Value">The <tt>Value</tt> class</a>
1666</div>
1667
1668<div>
1669
1670<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
1671<br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1672doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1673
1674<p>The <tt>Value</tt> class is the most important class in the LLVM Source
1675base. It represents a typed value that may be used (among other things) as an
1676operand to an instruction. There are many different types of <tt>Value</tt>s,
1677such as <a href="#Constant"><tt>Constant</tt></a>s,<a
1678href="#Argument"><tt>Argument</tt></a>s. Even <a
1679href="#Instruction"><tt>Instruction</tt></a>s and <a
1680href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
1681
1682<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
1683for a program. For example, an incoming argument to a function (represented
1684with an instance of the <a href="#Argument">Argument</a> class) is "used" by
1685every instruction in the function that references the argument. To keep track
1686of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
1687href="#User"><tt>User</tt></a>s that is using it (the <a
1688href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
1689graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
1690def-use information in the program, and is accessible through the <tt>use_</tt>*
1691methods, shown below.</p>
1692
1693<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
1694and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
1695method. In addition, all LLVM values can be named. The "name" of the
1696<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
1697
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1698<div class="doc_code">
1699<pre>
1700%<b>foo</b> = add int 1, 2
1701</pre>
1702</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1703
1704<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
1705that the name of any value may be missing (an empty string), so names should
1706<b>ONLY</b> be used for debugging (making the source code easier to read,
1707debugging printouts), they should not be used to keep track of values or map
1708between them. For this purpose, use a <tt>std::map</tt> of pointers to the
1709<tt>Value</tt> itself instead.</p>
1710
1711<p>One important aspect of LLVM is that there is no distinction between an SSA
1712variable and the operation that produces it. Because of this, any reference to
1713the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]1714argument, for example) is represented as a direct pointer to the instance of
1715the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1716represents this value. Although this may take some getting used to, it
1717simplifies the representation and makes it easier to manipulate.</p>
1718
1719</div>
1720
1721<!-- _______________________________________________________________________ -->
1722<div class="doc_subsubsection">
1723 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
1724</div>
1725
1726<div class="doc_text">
1727
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1728<ul>
1729 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
1730use-list<br>
1731 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
1732the use-list<br>
1733 <tt>unsigned use_size()</tt> - Returns the number of users of the
1734value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1735 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1736 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
1737the use-list.<br>
1738 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
1739use-list.<br>
1740 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
1741element in the list.
1742 <p> These methods are the interface to access the def-use
1743information in LLVM. As with all other iterators in LLVM, the naming
1744conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1745 </li>
1746 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1747 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1748 </li>
1749 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1750 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1751 <tt>void setName(const std::string &amp;Name)</tt>
1752 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
1753be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1754 </li>
1755 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1756
1757 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
1758 href="#User"><tt>User</tt>s</a> of the current value to refer to
1759 "<tt>V</tt>" instead. For example, if you detect that an instruction always
1760 produces a constant value (for example through constant folding), you can
1761 replace all uses of the instruction with the constant like this:</p>
1762
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1763<div class="doc_code">
1764<pre>
1765Inst-&gt;replaceAllUsesWith(ConstVal);
1766</pre>
1767</div>
1768
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1769</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1770
1771</div>
1772
1773<!-- ======================================================================= -->
1774<div class="doc_subsection">
1775 <a name="User">The <tt>User</tt> class</a>
1776</div>
1777
1778<div class="doc_text">
1779
1780<p>
1781<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]1782doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1783Superclass: <a href="#Value"><tt>Value</tt></a></p>
1784
1785<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
1786refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1787that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1788referring to. The <tt>User</tt> class itself is a subclass of
1789<tt>Value</tt>.</p>
1790
1791<p>The operands of a <tt>User</tt> point directly to the LLVM <a
1792href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1793Single Assignment (SSA) form, there can only be one definition referred to,
1794allowing this direct connection. This connection provides the use-def
1795information in LLVM.</p>
1796
1797</div>
1798
1799<!-- _______________________________________________________________________ -->
1800<div class="doc_subsubsection">
1801 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
1802</div>
1803
1804<div class="doc_text">
1805
1806<p>The <tt>User</tt> class exposes the operand list in two ways: through
1807an index access interface and through an iterator based interface.</p>
1808
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1809<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1810 <li><tt>Value *getOperand(unsigned i)</tt><br>
1811 <tt>unsigned getNumOperands()</tt>
1812 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1813convenient form for direct access.</p></li>
1814
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1815 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
1816list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1817 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
1818the operand list.<br>
1819 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1820operand list.
1821 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1822the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1823</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1824
1825</div>
1826
1827<!-- ======================================================================= -->
1828<div class="doc_subsection">
1829 <a name="Instruction">The <tt>Instruction</tt> class</a>
1830</div>
1831
1832<div class="doc_text">
1833
1834<p><tt>#include "</tt><tt><a
1835href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1836doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1837Superclasses: <a href="#User"><tt>User</tt></a>, <a
1838href="#Value"><tt>Value</tt></a></p>
1839
1840<p>The <tt>Instruction</tt> class is the common base class for all LLVM
1841instructions. It provides only a few methods, but is a very commonly used
1842class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1843opcode (instruction type) and the parent <a
1844href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1845into. To represent a specific type of instruction, one of many subclasses of
1846<tt>Instruction</tt> are used.</p>
1847
1848<p> Because the <tt>Instruction</tt> class subclasses the <a
1849href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1850way as for other <a href="#User"><tt>User</tt></a>s (with the
1851<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1852<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
1853the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
1854file contains some meta-data about the various different types of instructions
1855in LLVM. It describes the enum values that are used as opcodes (for example
1856<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
1857concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
1858example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1859href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1860this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1861<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1862
1863</div>
1864
1865<!-- _______________________________________________________________________ -->
1866<div class="doc_subsubsection">
1867 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
1868 class</a>
1869</div>
1870
1871<div class="doc_text">
1872
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1873<ul>
1874 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1875 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
1876this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1877 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1878 <p>Returns true if the instruction writes to memory, i.e. it is a
1879 <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]1880 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1881 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1882 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1883 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1884in all ways to the original except that the instruction has no parent
1885(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1886and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1887</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1888
1889</div>
1890
1891<!-- ======================================================================= -->
1892<div class="doc_subsection">
1893 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1894</div>
1895
1896<div class="doc_text">
1897
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1898<p><tt>#include "<a
1899href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
1900doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
1901Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1902Superclass: <a href="#Value"><tt>Value</tt></a></p>
1903
1904<p>This class represents a single entry multiple exit section of the code,
1905commonly known as a basic block by the compiler community. The
1906<tt>BasicBlock</tt> class maintains a list of <a
1907href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
1908Matching the language definition, the last element of this list of instructions
1909is always a terminator instruction (a subclass of the <a
1910href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
1911
1912<p>In addition to tracking the list of instructions that make up the block, the
1913<tt>BasicBlock</tt> class also keeps track of the <a
1914href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
1915
1916<p>Note that <tt>BasicBlock</tt>s themselves are <a
1917href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1918like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1919<tt>label</tt>.</p>
1920
1921</div>
1922
1923<!-- _______________________________________________________________________ -->
1924<div class="doc_subsubsection">
1925 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
1926 class</a>
1927</div>
1928
1929<div class="doc_text">
1930
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1931<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1932
1933<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1934 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1935
1936<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1937insertion into a function. The constructor optionally takes a name for the new
1938block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
1939the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
1940automatically inserted at the end of the specified <a
1941href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1942manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
1943
1944<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1945<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1946<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1947<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1948STL-style functions for accessing the instruction list.
1949
1950<p>These methods and typedefs are forwarding functions that have the same
1951semantics as the standard library methods of the same names. These methods
1952expose the underlying instruction list of a basic block in a way that is easy to
1953manipulate. To get the full complement of container operations (including
1954operations to update the list), you must use the <tt>getInstList()</tt>
1955method.</p></li>
1956
1957<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
1958
1959<p>This method is used to get access to the underlying container that actually
1960holds the Instructions. This method must be used when there isn't a forwarding
1961function in the <tt>BasicBlock</tt> class for the operation that you would like
1962to perform. Because there are no forwarding functions for "updating"
1963operations, you need to use this if you want to update the contents of a
1964<tt>BasicBlock</tt>.</p></li>
1965
1966<li><tt><a href="#Function">Function</a> *getParent()</tt>
1967
1968<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1969embedded into, or a null pointer if it is homeless.</p></li>
1970
1971<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
1972
1973<p> Returns a pointer to the terminator instruction that appears at the end of
1974the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1975instruction in the block is not a terminator, then a null pointer is
1976returned.</p></li>
1977
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1978</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1979
1980</div>
1981
1982<!-- ======================================================================= -->
1983<div class="doc_subsection">
1984 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1985</div>
1986
1987<div class="doc_text">
1988
1989<p><tt>#include "<a
1990href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1991doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
1992Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]1993Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
1994<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]1995
1996<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1997href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1998visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1999Because they are visible at global scope, they are also subject to linking with
2000other globals defined in different translation units. To control the linking
2001process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
2002<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2003defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2004
2005<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
2006<tt>static</tt> in C), it is not visible to code outside the current translation
2007unit, and does not participate in linking. If it has external linkage, it is
2008visible to external code, and does participate in linking. In addition to
2009linkage information, <tt>GlobalValue</tt>s keep track of which <a
2010href="#Module"><tt>Module</tt></a> they are currently part of.</p>
2011
2012<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
2013by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
2014global is always a pointer to its contents. It is important to remember this
2015when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
2016be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
2017subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
2018int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
2019the address of the first element of this array and the value of the
2020<tt>GlobalVariable</tt> are the same, they have different types. The
2021<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
2022is <tt>int.</tt> Because of this, accessing a global value requires you to
2023dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
2024can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
2025Language Reference Manual</a>.</p>
2026
2027</div>
2028
2029<!-- _______________________________________________________________________ -->
2030<div class="doc_subsubsection">
2031 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
2032 class</a>
2033</div>
2034
2035<div class="doc_text">
2036
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2037<ul>
2038 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2039 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2040 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
2041 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
2042 <p> </p>
2043 </li>
2044 <li><tt><a href="#Module">Module</a> *getParent()</tt>
2045 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2046GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2047</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2048
2049</div>
2050
2051<!-- ======================================================================= -->
2052<div class="doc_subsection">
2053 <a name="Function">The <tt>Function</tt> class</a>
2054</div>
2055
2056<div class="doc_text">
2057
2058<p><tt>#include "<a
2059href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2060info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2061Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2062<a href="#Constant"><tt>Constant</tt></a>,
2063<a href="#User"><tt>User</tt></a>,
2064<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2065
2066<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
2067actually one of the more complex classes in the LLVM heirarchy because it must
2068keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2069of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
2070<a href="#Argument"><tt>Argument</tt></a>s, and a
2071<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2072
2073<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
2074commonly used part of <tt>Function</tt> objects. The list imposes an implicit
2075ordering of the blocks in the function, which indicate how the code will be
2076layed out by the backend. Additionally, the first <a
2077href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
2078<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
2079block. There are no implicit exit nodes, and in fact there may be multiple exit
2080nodes from a single <tt>Function</tt>. If the <a
2081href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
2082the <tt>Function</tt> is actually a function declaration: the actual body of the
2083function hasn't been linked in yet.</p>
2084
2085<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
2086<tt>Function</tt> class also keeps track of the list of formal <a
2087href="#Argument"><tt>Argument</tt></a>s that the function receives. This
2088container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
2089nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
2090the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
2091
2092<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
2093LLVM feature that is only used when you have to look up a value by name. Aside
2094from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
2095internally to make sure that there are not conflicts between the names of <a
2096href="#Instruction"><tt>Instruction</tt></a>s, <a
2097href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
2098href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
2099
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2100<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
2101and therefore also a <a href="#Constant">Constant</a>. The value of the function
2102is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2103</div>
2104
2105<!-- _______________________________________________________________________ -->
2106<div class="doc_subsubsection">
2107 <a name="m_Function">Important Public Members of the <tt>Function</tt>
2108 class</a>
2109</div>
2110
2111<div class="doc_text">
2112
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2113<ul>
2114 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2115 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2116
2117 <p>Constructor used when you need to create new <tt>Function</tt>s to add
2118 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2119 create and what type of linkage the function should have. The <a
2120 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2121 specifies the formal arguments and return value for the function. The same
2122 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
2123 create multiple functions. The <tt>Parent</tt> argument specifies the Module
2124 in which the function is defined. If this argument is provided, the function
2125 will automatically be inserted into that module's list of
2126 functions.</p></li>
2127
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2128 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2129
2130 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
2131 function is "external", it does not have a body, and thus must be resolved
2132 by linking with a function defined in a different translation unit.</p></li>
2133
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2134 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2135 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2136
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2137 <tt>begin()</tt>, <tt>end()</tt>
2138 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2139
2140 <p>These are forwarding methods that make it easy to access the contents of
2141 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
2142 list.</p></li>
2143
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2144 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2145
2146 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
2147 is necessary to use when you need to update the list or perform a complex
2148 action that doesn't have a forwarding method.</p></li>
2149
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2150 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2151iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2152 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2153
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2154 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2155 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2156
2157 <p>These are forwarding methods that make it easy to access the contents of
2158 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
2159 list.</p></li>
2160
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2161 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2162
2163 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
2164 necessary to use when you need to update the list or perform a complex
2165 action that doesn't have a forwarding method.</p></li>
2166
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2167 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2168
2169 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
2170 function. Because the entry block for the function is always the first
2171 block, this returns the first block of the <tt>Function</tt>.</p></li>
2172
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2173 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
2174 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2175
2176 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
2177 <tt>Function</tt> and returns the return type of the function, or the <a
2178 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
2179 function.</p></li>
2180
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2181 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2182
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2183 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2184 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2185</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2186
2187</div>
2188
2189<!-- ======================================================================= -->
2190<div class="doc_subsection">
2191 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
2192</div>
2193
2194<div class="doc_text">
2195
2196<p><tt>#include "<a
2197href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
2198<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2199doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2200 Class</a><br>
2201Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2202<a href="#Constant"><tt>Constant</tt></a>,
2203<a href="#User"><tt>User</tt></a>,
2204<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2205
2206<p>Global variables are represented with the (suprise suprise)
2207<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
2208subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
2209always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2210"name" refers to their constant address). See
2211<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
2212variables may have an initial value (which must be a
2213<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
2214they may be marked as "constant" themselves (indicating that their contents
2215never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2216</div>
2217
2218<!-- _______________________________________________________________________ -->
2219<div class="doc_subsubsection">
2220 <a name="m_GlobalVariable">Important Public Members of the
2221 <tt>GlobalVariable</tt> class</a>
2222</div>
2223
2224<div class="doc_text">
2225
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2226<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2227 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
2228 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
2229 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
2230
2231 <p>Create a new global variable of the specified type. If
2232 <tt>isConstant</tt> is true then the global variable will be marked as
2233 unchanging for the program. The Linkage parameter specifies the type of
2234 linkage (internal, external, weak, linkonce, appending) for the variable. If
2235 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
2236 the resultant global variable will have internal linkage. AppendingLinkage
2237 concatenates together all instances (in different translation units) of the
2238 variable into a single variable but is only applicable to arrays. &nbsp;See
2239 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
2240 further details on linkage types. Optionally an initializer, a name, and the
2241 module to put the variable into may be specified for the global variable as
2242 well.</p></li>
2243
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2244 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2245
2246 <p>Returns true if this is a global variable that is known not to
2247 be modified at runtime.</p></li>
2248
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2249 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2250
2251 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
2252
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2253 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2254
2255 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
2256 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2257</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2258
2259</div>
2260
2261<!-- ======================================================================= -->
2262<div class="doc_subsection">
2263 <a name="Module">The <tt>Module</tt> class</a>
2264</div>
2265
2266<div class="doc_text">
2267
2268<p><tt>#include "<a
2269href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2270<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2271
2272<p>The <tt>Module</tt> class represents the top level structure present in LLVM
2273programs. An LLVM module is effectively either a translation unit of the
2274original program or a combination of several translation units merged by the
2275linker. The <tt>Module</tt> class keeps track of a list of <a
2276href="#Function"><tt>Function</tt></a>s, a list of <a
2277href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
2278href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
2279helpful member functions that try to make common operations easy.</p>
2280
2281</div>
2282
2283<!-- _______________________________________________________________________ -->
2284<div class="doc_subsubsection">
2285 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
2286</div>
2287
2288<div class="doc_text">
2289
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2290<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2291 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2292</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2293
2294<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
2295provide a name for it (probably based on the name of the translation unit).</p>
2296
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2297<ul>
2298 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]2299 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2300
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2301 <tt>begin()</tt>, <tt>end()</tt>
2302 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2303
2304 <p>These are forwarding methods that make it easy to access the contents of
2305 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
2306 list.</p></li>
2307
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2308 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2309
2310 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
2311 necessary to use when you need to update the list or perform a complex
2312 action that doesn't have a forwarding method.</p>
2313
2314 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2315</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2316
2317<hr>
2318
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2319<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2320 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2321
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2322 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2323
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2324 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2325 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2326
2327 <p> These are forwarding methods that make it easy to access the contents of
2328 a <tt>Module</tt> object's <a
2329 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
2330
2331 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
2332
2333 <p>Returns the list of <a
2334 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2335 use when you need to update the list or perform a complex action that
2336 doesn't have a forwarding method.</p>
2337
2338 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2339</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2340
2341<hr>
2342
2343<ul>
2344 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2345
2346 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2347 for this <tt>Module</tt>.</p>
2348
2349 <p><!-- Convenience methods --></p></li>
2350</ul>
2351
2352<hr>
2353
2354<ul>
2355 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2356 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2357
2358 <p>Look up the specified function in the <tt>Module</tt> <a
2359 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2360 <tt>null</tt>.</p></li>
2361
2362 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2363 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2364
2365 <p>Look up the specified function in the <tt>Module</tt> <a
2366 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2367 external declaration for the function and return it.</p></li>
2368
2369 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2370
2371 <p>If there is at least one entry in the <a
2372 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2373 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2374 string.</p></li>
2375
2376 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
2377 href="#Type">Type</a> *Ty)</tt>
2378
2379 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2380 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2381 name, true is returned and the <a
2382 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2383</ul>
2384
2385</div>
2386
2387<!-- ======================================================================= -->
2388<div class="doc_subsection">
2389 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2390</div>
2391
2392<div class="doc_text">
2393
2394<p>Constant represents a base class for different types of constants. It
2395is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
2396ConstantArray etc for representing the various types of Constants.</p>
2397
2398</div>
2399
2400<!-- _______________________________________________________________________ -->
2401<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2402 <a name="m_Constant">Important Public Methods</a>
2403</div>
2404<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2405</div>
2406
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2407<!-- _______________________________________________________________________ -->
2408<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2409<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2410<ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2411 <li>ConstantSInt : This subclass of Constant represents a signed integer
2412 constant.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2413 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2414 <li><tt>int64_t getValue() const</tt>: Returns the underlying value of
2415 this constant. </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2416 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2417 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2418 <li>ConstantUInt : This class represents an unsigned integer.
2419 <ul>
2420 <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
2421 this constant. </li>
2422 </ul>
2423 </li>
2424 <li>ConstantFP : This class represents a floating point constant.
2425 <ul>
2426 <li><tt>double getValue() const</tt>: Returns the underlying value of
2427 this constant. </li>
2428 </ul>
2429 </li>
2430 <li>ConstantBool : This represents a boolean constant.
2431 <ul>
2432 <li><tt>bool getValue() const</tt>: Returns the underlying value of this
2433 constant. </li>
2434 </ul>
2435 </li>
2436 <li>ConstantArray : This represents a constant array.
2437 <ul>
2438 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2439 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2440 </ul>
2441 </li>
2442 <li>ConstantStruct : This represents a constant struct.
2443 <ul>
2444 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2445 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2446 </ul>
2447 </li>
2448 <li>GlobalValue : This represents either a global variable or a function. In
2449 either case, the value is a constant fixed address (after linking).
2450 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2451</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2452</div>
2453
2454<!-- ======================================================================= -->
2455<div class="doc_subsection">
2456 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
2457</div>
2458
2459<div class="doc_text">
2460
2461<p>Type as noted earlier is also a subclass of a Value class. Any primitive
2462type (like int, short etc) in LLVM is an instance of Type Class. All other
2463types are instances of subclasses of type like FunctionType, ArrayType
2464etc. DerivedType is the interface for all such dervied types including
2465FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
2466be recursive (StructType). There exists exactly one instance of any type
2467structure at a time. This allows using pointer equality of Type *s for comparing
2468types.</p>
2469
2470</div>
2471
2472<!-- _______________________________________________________________________ -->
2473<div class="doc_subsubsection">
2474 <a name="m_Value">Important Public Methods</a>
2475</div>
2476
2477<div class="doc_text">
2478
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2479<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2480
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2481 <li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
2482 is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
2483 not true for Float and Double. </li>
2484
2485 <li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
2486 unsigned. This is not quite the complement of isSigned... nonnumeric types
2487 return false as they do with isSigned. This returns true for UByteTy,
2488 UShortTy, UIntTy, and ULongTy. </li>
2489
Chris Lattner4573f1b2004-07-08 17:49:37 +0000[diff] [blame]2490 <li><tt>bool isInteger() const</tt>: Equivalent to isSigned() || isUnsigned().</li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2491
2492 <li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
2493 type, which is either Bool type or one of the Integer types.</li>
2494
2495 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
2496 floating point types.</li>
2497
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2498 <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
2499 this type can be converted to 'Ty' without any reinterpretation of bits. For
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2500 example, uint to int or one pointer type to another.</li>
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2501</ul>
2502</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2503
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2504<!-- _______________________________________________________________________ -->
2505<div class="doc_subsubsection">
2506 <a name="m_Value">Important Derived Types</a>
2507</div>
2508<div class="doc_text">
2509<ul>
2510 <li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2511 <ul>
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2512 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2513 of the elements in the sequential type. </li>
2514 </ul>
2515 </li>
2516 <li>ArrayType : This is a subclass of SequentialType and defines interface for
2517 array types.
2518 <ul>
2519 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2520 elements in the array. </li>
2521 </ul>
2522 </li>
2523 <li>PointerType : Subclass of SequentialType for pointer types. </li>
2524 <li>StructType : subclass of DerivedTypes for struct types </li>
2525 <li>FunctionType : subclass of DerivedTypes for function types.
2526 <ul>
2527 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2528 function</li>
2529 <li><tt> const Type * getReturnType() const</tt>: Returns the
2530 return type of the function.</li>
2531 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2532 the type of the ith parameter.</li>
2533 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2534 number of formal parameters.</li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2535 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2536 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2537</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2538</div>
2539
2540<!-- ======================================================================= -->
2541<div class="doc_subsection">
2542 <a name="Argument">The <tt>Argument</tt> class</a>
2543</div>
2544
2545<div class="doc_text">
2546
2547<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2548arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2549arguments. An argument has a pointer to the parent Function.</p>
2550
2551</div>
2552
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2553<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2554<hr>
2555<address>
2556 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
2557 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
2558 <a href="http://validator.w3.org/check/referer"><img
2559 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
2560
2561 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2562 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2563 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2564 Last modified: $Date$
2565</address>
2566
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2567</body>
2568</html>