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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 Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]306 // <i>Otherwise, it must be an instruction...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]307 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
308}
309</pre>
310</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]311
312 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
313 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
314 operator.</p>
315
316 </dd>
317
318 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
319
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]320 <dd><p>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation.
321 It checks to see if the operand is of the specified type, and if so, returns a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]322 pointer to it (this operator does not work with references). If the operand is
323 not of the correct type, a null pointer is returned. Thus, this works very
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]324 much like the <tt>dynamic_cast&lt;&gt;</tt> operator in C++, and should be
325 used in the same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt>
326 operator is used in an <tt>if</tt> statement or some other flow control
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]327 statement like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]328
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]329<div class="doc_code">
330<pre>
331if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]332 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]333}
334</pre>
335</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]336
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]337 <p>This form of the <tt>if</tt> statement effectively combines together a call
338 to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
339 statement, which is very convenient.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]340
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]341 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
342 <tt>dynamic_cast&lt;&gt;</tt> or Java's <tt>instanceof</tt> operator, can be
343 abused. In particular, you should not use big chained <tt>if/then/else</tt>
344 blocks to check for lots of different variants of classes. If you find
345 yourself wanting to do this, it is much cleaner and more efficient to use the
346 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]347
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]348 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]349
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]350 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
351
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]352 <dd><p>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]353 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as an
354 argument (which it then propagates). This can sometimes be useful, allowing
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]355 you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]356
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]357 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]358
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]359 <dd><p>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]360 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
361 as an argument (which it then propagates). This can sometimes be useful,
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]362 allowing you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]363
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]364</dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]365
366<p>These five templates can be used with any classes, whether they have a
367v-table or not. To add support for these templates, you simply need to add
368<tt>classof</tt> static methods to the class you are interested casting
369to. Describing this is currently outside the scope of this document, but there
370are lots of examples in the LLVM source base.</p>
371
372</div>
373
374<!-- ======================================================================= -->
375<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]376 <a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]377</div>
378
379<div class="doc_text">
380
381<p>Often when working on your pass you will put a bunch of debugging printouts
382and other code into your pass. After you get it working, you want to remove
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]383it, but you may need it again in the future (to work out new bugs that you run
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]384across).</p>
385
386<p> Naturally, because of this, you don't want to delete the debug printouts,
387but you don't want them to always be noisy. A standard compromise is to comment
388them out, allowing you to enable them if you need them in the future.</p>
389
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]390<p>The "<tt><a href="/doxygen/Debug_8h-source.html">llvm/Support/Debug.h</a></tt>"
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]391file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
392this problem. Basically, you can put arbitrary code into the argument of the
393<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
394tool) is run with the '<tt>-debug</tt>' command line argument:</p>
395
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]396<div class="doc_code">
397<pre>
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
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]407<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]408$ opt &lt; a.bc &gt; /dev/null -mypass -debug
409I am here!
410</pre>
411</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]412
413<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
414to not have to create "yet another" command line option for the debug output for
415your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
416so they do not cause a performance impact at all (for the same reason, they
417should also not contain side-effects!).</p>
418
419<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
420enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
421"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
422program hasn't been started yet, you can always just run it with
423<tt>-debug</tt>.</p>
424
425</div>
426
427<!-- _______________________________________________________________________ -->
428<div class="doc_subsubsection">
Chris Lattnerc9151082005-04-26 22:57:07 +0000[diff] [blame]429 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]430 the <tt>-debug-only</tt> option</a>
431</div>
432
433<div class="doc_text">
434
435<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
436just turns on <b>too much</b> information (such as when working on the code
437generator). If you want to enable debug information with more fine-grained
438control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
439option as follows:</p>
440
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]441<div class="doc_code">
442<pre>
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
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]461<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]462$ opt &lt; a.bc &gt; /dev/null -mypass -debug
463No debug type
464'foo' debug type
465'bar' debug type
466No debug type (2)
467$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo
468'foo' debug type
469$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar
470'bar' debug type
471</pre>
472</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]473
474<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
475a file, to specify the debug type for the entire module (if you do this before
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]476you <tt>#include "llvm/Support/Debug.h"</tt>, you don't have to insert the ugly
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]477<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
478"bar", because there is no system in place to ensure that names do not
479conflict. If two different modules use the same string, they will all be turned
480on when the name is specified. This allows, for example, all debug information
481for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]482even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]483
484</div>
485
486<!-- ======================================================================= -->
487<div class="doc_subsection">
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>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]528++NumXForms; // <i>I did stuff!</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]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
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]541<i>... statistics output ...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]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>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]694// <i>func is a pointer to a Function instance</i>
695for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i)
696 // <i>Print out the name of the basic block if it has one, and then the</i>
697 // <i>number of instructions that it contains</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]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";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]700</pre>
701</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]702
703<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]704invoking member functions of the <tt>Instruction</tt> class. This is
705because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]706classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]707exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
708
709</div>
710
711<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]712<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]713 <a name="iterate_basicblock">Iterating over the </a><a
714 href="#Instruction"><tt>Instruction</tt></a>s in a <a
715 href="#BasicBlock"><tt>BasicBlock</tt></a>
716</div>
717
718<div class="doc_text">
719
720<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
721easy to iterate over the individual instructions that make up
722<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
723a <tt>BasicBlock</tt>:</p>
724
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]725<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]726<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]727// <i>blk is a pointer to a BasicBlock instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]728for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]729 // <i>The next statement works since operator&lt;&lt;(ostream&amp;,...)</i>
730 // <i>is overloaded for Instruction&amp;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]731 std::cerr &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]732</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]733</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]734
735<p>However, this isn't really the best way to print out the contents of a
736<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
737anything you'll care about, you could have just invoked the print routine on the
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]738basic block itself: <tt>std::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]739
740</div>
741
742<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]743<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]744 <a name="iterate_institer">Iterating over the </a><a
745 href="#Instruction"><tt>Instruction</tt></a>s in a <a
746 href="#Function"><tt>Function</tt></a>
747</div>
748
749<div class="doc_text">
750
751<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
752<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
753<tt>InstIterator</tt> should be used instead. You'll need to include <a
754href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
755and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]756small 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]757
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]758<div class="doc_code">
759<pre>
760#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
761
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]762// <i>F is a ptr to a Function instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]763for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
764 std::cerr &lt;&lt; *i &lt;&lt; "\n";
765</pre>
766</div>
767
768<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]769worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]770initialize a worklist to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]771F, all you would need to do is something like:</p>
772
773<div class="doc_code">
774<pre>
775std::set&lt;Instruction*&gt; worklist;
776worklist.insert(inst_begin(F), inst_end(F));
777</pre>
778</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]779
780<p>The STL set <tt>worklist</tt> would now contain all instructions in the
781<tt>Function</tt> pointed to by F.</p>
782
783</div>
784
785<!-- _______________________________________________________________________ -->
786<div class="doc_subsubsection">
787 <a name="iterate_convert">Turning an iterator into a class pointer (and
788 vice-versa)</a>
789</div>
790
791<div class="doc_text">
792
793<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]794instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]795a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]796Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]797is a <tt>BasicBlock::const_iterator</tt>:</p>
798
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]799<div class="doc_code">
800<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]801Instruction&amp; inst = *i; // <i>Grab reference to instruction reference</i>
802Instruction* pinst = &amp;*i; // <i>Grab pointer to instruction reference</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]803const Instruction&amp; inst = *j;
804</pre>
805</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]806
807<p>However, the iterators you'll be working with in the LLVM framework are
808special: they will automatically convert to a ptr-to-instance type whenever they
809need to. Instead of dereferencing the iterator and then taking the address of
810the result, you can simply assign the iterator to the proper pointer type and
811you get the dereference and address-of operation as a result of the assignment
812(behind the scenes, this is a result of overloading casting mechanisms). Thus
813the last line of the last example,</p>
814
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]815<div class="doc_code">
816<pre>
817Instruction* pinst = &amp;*i;
818</pre>
819</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]820
821<p>is semantically equivalent to</p>
822
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]823<div class="doc_code">
824<pre>
825Instruction* pinst = i;
826</pre>
827</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]828
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]829<p>It's also possible to turn a class pointer into the corresponding iterator,
830and this is a constant time operation (very efficient). The following code
831snippet illustrates use of the conversion constructors provided by LLVM
832iterators. By using these, you can explicitly grab the iterator of something
833without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]834
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]835<div class="doc_code">
836<pre>
837void printNextInstruction(Instruction* inst) {
838 BasicBlock::iterator it(inst);
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]839 ++it; // <i>After this line, it refers to the instruction after *inst</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]840 if (it != inst-&gt;getParent()-&gt;end()) std::cerr &lt;&lt; *it &lt;&lt; "\n";
841}
842</pre>
843</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]844
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]845</div>
846
847<!--_______________________________________________________________________-->
848<div class="doc_subsubsection">
849 <a name="iterate_complex">Finding call sites: a slightly more complex
850 example</a>
851</div>
852
853<div class="doc_text">
854
855<p>Say that you're writing a FunctionPass and would like to count all the
856locations in the entire module (that is, across every <tt>Function</tt>) where a
857certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
858learn 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]859much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]860you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
861is what we want to do:</p>
862
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]863<div class="doc_code">
864<pre>
865initialize callCounter to zero
866for each Function f in the Module
867 for each BasicBlock b in f
868 for each Instruction i in b
869 if (i is a CallInst and calls the given function)
870 increment callCounter
871</pre>
872</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]873
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]874<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]875<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]876override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]877
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]878<div class="doc_code">
879<pre>
880Function* targetFunc = ...;
881
882class OurFunctionPass : public FunctionPass {
883 public:
884 OurFunctionPass(): callCounter(0) { }
885
886 virtual runOnFunction(Function&amp; F) {
887 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
888 for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
889 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
890 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]891 // <i>We know we've encountered a call instruction, so we</i>
892 // <i>need to determine if it's a call to the</i>
893 // <i>function pointed to by m_func or not</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]894
895 if (callInst-&gt;getCalledFunction() == targetFunc)
896 ++callCounter;
897 }
898 }
899 }
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]900 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]901
902 private:
903 unsigned callCounter;
904};
905</pre>
906</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]907
908</div>
909
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]910<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]911<div class="doc_subsubsection">
912 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
913</div>
914
915<div class="doc_text">
916
917<p>You may have noticed that the previous example was a bit oversimplified in
918that it did not deal with call sites generated by 'invoke' instructions. In
919this, and in other situations, you may find that you want to treat
920<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
921most-specific common base class is <tt>Instruction</tt>, which includes lots of
922less closely-related things. For these cases, LLVM provides a handy wrapper
923class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]924href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]925It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
926methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]927<tt>InvokeInst</tt>s.</p>
928
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]929<p>This class has "value semantics": it should be passed by value, not by
930reference and it should not be dynamically allocated or deallocated using
931<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
932assignable and constructable, with costs equivalents to that of a bare pointer.
933If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]934
935</div>
936
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]937<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]938<div class="doc_subsubsection">
939 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
940</div>
941
942<div class="doc_text">
943
944<p>Frequently, we might have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]945href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
946determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
947<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
948For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
949particular function <tt>foo</tt>. Finding all of the instructions that
950<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
951of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]952
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]953<div class="doc_code">
954<pre>
955Function* F = ...;
956
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]957for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i)
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]958 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
959 std::cerr &lt;&lt; "F is used in instruction:\n";
960 std::cerr &lt;&lt; *Inst &lt;&lt; "\n";
961 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]962</pre>
963</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]964
965<p>Alternately, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]966href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]967<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
968<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
969<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
970all of the values that a particular instruction uses (that is, the operands of
971the particular <tt>Instruction</tt>):</p>
972
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]973<div class="doc_code">
974<pre>
975Instruction* pi = ...;
976
977for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {
978 Value* v = *i;
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]979 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]980}
981</pre>
982</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]983
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]984<!--
985 def-use chains ("finding all users of"): Value::use_begin/use_end
986 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]987-->
988
989</div>
990
991<!-- ======================================================================= -->
992<div class="doc_subsection">
993 <a name="simplechanges">Making simple changes</a>
994</div>
995
996<div class="doc_text">
997
998<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]999infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1000transformations, it's fairly common to manipulate the contents of basic
1001blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1002and gives example code.</p>
1003
1004</div>
1005
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1006<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1007<div class="doc_subsubsection">
1008 <a name="schanges_creating">Creating and inserting new
1009 <tt>Instruction</tt>s</a>
1010</div>
1011
1012<div class="doc_text">
1013
1014<p><i>Instantiating Instructions</i></p>
1015
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1016<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1017constructor for the kind of instruction to instantiate and provide the necessary
1018parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
1019(const-ptr-to) <tt>Type</tt>. Thus:</p>
1020
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1021<div class="doc_code">
1022<pre>
1023AllocaInst* ai = new AllocaInst(Type::IntTy);
1024</pre>
1025</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1026
1027<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
1028one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
1029subclass is likely to have varying default parameters which change the semantics
1030of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1031href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1032Instruction</a> that you're interested in instantiating.</p>
1033
1034<p><i>Naming values</i></p>
1035
1036<p>It is very useful to name the values of instructions when you're able to, as
1037this facilitates the debugging of your transformations. If you end up looking
1038at generated LLVM machine code, you definitely want to have logical names
1039associated with the results of instructions! By supplying a value for the
1040<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
1041associate a logical name with the result of the instruction's execution at
1042runtime. For example, say that I'm writing a transformation that dynamically
1043allocates space for an integer on the stack, and that integer is going to be
1044used as some kind of index by some other code. To accomplish this, I place an
1045<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
1046<tt>Function</tt>, and I'm intending to use it within the same
1047<tt>Function</tt>. I might do:</p>
1048
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1049<div class="doc_code">
1050<pre>
1051AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");
1052</pre>
1053</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1054
1055<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
1056execution value, which is a pointer to an integer on the runtime stack.</p>
1057
1058<p><i>Inserting instructions</i></p>
1059
1060<p>There are essentially two ways to insert an <tt>Instruction</tt>
1061into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
1062
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]1063<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1064 <li>Insertion into an explicit instruction list
1065
1066 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
1067 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
1068 before <tt>*pi</tt>, we do the following: </p>
1069
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1070<div class="doc_code">
1071<pre>
1072BasicBlock *pb = ...;
1073Instruction *pi = ...;
1074Instruction *newInst = new Instruction(...);
1075
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1076pb-&gt;getInstList().insert(pi, newInst); // <i>Inserts newInst before pi in pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1077</pre>
1078</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1079
1080 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
1081 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
1082 classes provide constructors which take a pointer to a
1083 <tt>BasicBlock</tt> to be appended to. For example code that
1084 looked like: </p>
1085
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1086<div class="doc_code">
1087<pre>
1088BasicBlock *pb = ...;
1089Instruction *newInst = new Instruction(...);
1090
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1091pb-&gt;getInstList().push_back(newInst); // <i>Appends newInst to pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1092</pre>
1093</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1094
1095 <p>becomes: </p>
1096
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1097<div class="doc_code">
1098<pre>
1099BasicBlock *pb = ...;
1100Instruction *newInst = new Instruction(..., pb);
1101</pre>
1102</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1103
1104 <p>which is much cleaner, especially if you are creating
1105 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1106
1107 <li>Insertion into an implicit instruction list
1108
1109 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
1110 are implicitly associated with an existing instruction list: the instruction
1111 list of the enclosing basic block. Thus, we could have accomplished the same
1112 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
1113 </p>
1114
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1115<div class="doc_code">
1116<pre>
1117Instruction *pi = ...;
1118Instruction *newInst = new Instruction(...);
1119
1120pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);
1121</pre>
1122</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1123
1124 <p>In fact, this sequence of steps occurs so frequently that the
1125 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
1126 constructors which take (as a default parameter) a pointer to an
1127 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
1128 precede. That is, <tt>Instruction</tt> constructors are capable of
1129 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
1130 provided instruction, immediately before that instruction. Using an
1131 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
1132 parameter, the above code becomes:</p>
1133
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1134<div class="doc_code">
1135<pre>
1136Instruction* pi = ...;
1137Instruction* newInst = new Instruction(..., pi);
1138</pre>
1139</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1140
1141 <p>which is much cleaner, especially if you're creating a lot of
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1142 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1143</ul>
1144
1145</div>
1146
1147<!--_______________________________________________________________________-->
1148<div class="doc_subsubsection">
1149 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
1150</div>
1151
1152<div class="doc_text">
1153
1154<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1155<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1156you must have a pointer to the instruction that you wish to delete. Second, you
1157need to obtain the pointer to that instruction's basic block. You use the
1158pointer to the basic block to get its list of instructions and then use the
1159erase function to remove your instruction. For example:</p>
1160
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1161<div class="doc_code">
1162<pre>
1163<a href="#Instruction">Instruction</a> *I = .. ;
1164<a href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();
1165
1166BB-&gt;getInstList().erase(I);
1167</pre>
1168</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1169
1170</div>
1171
1172<!--_______________________________________________________________________-->
1173<div class="doc_subsubsection">
1174 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
1175 <tt>Value</tt></a>
1176</div>
1177
1178<div class="doc_text">
1179
1180<p><i>Replacing individual instructions</i></p>
1181
1182<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]1183permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1184and <tt>ReplaceInstWithInst</tt>.</p>
1185
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1186<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1187
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1188<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1189 <li><tt>ReplaceInstWithValue</tt>
1190
1191 <p>This function replaces all uses (within a basic block) of a given
1192 instruction with a value, and then removes the original instruction. The
1193 following example illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1194 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1195 pointer to an integer.</p>
1196
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1197<div class="doc_code">
1198<pre>
1199AllocaInst* instToReplace = ...;
1200BasicBlock::iterator ii(instToReplace);
1201
1202ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1203 Constant::getNullValue(PointerType::get(Type::IntTy)));
1204</pre></div></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1205
1206 <li><tt>ReplaceInstWithInst</tt>
1207
1208 <p>This function replaces a particular instruction with another
1209 instruction. The following example illustrates the replacement of one
1210 <tt>AllocaInst</tt> with another.</p>
1211
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1212<div class="doc_code">
1213<pre>
1214AllocaInst* instToReplace = ...;
1215BasicBlock::iterator ii(instToReplace);
1216
1217ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1218 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));
1219</pre></div></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1220</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1221
1222<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
1223
1224<p>You can use <tt>Value::replaceAllUsesWith</tt> and
1225<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]1226doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
1227and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1228information.</p>
1229
1230<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
1231include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
1232ReplaceInstWithValue, ReplaceInstWithInst -->
1233
1234</div>
1235
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1236<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1237<div class="doc_section">
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1238 <a name="advanced">Advanced Topics</a>
1239</div>
1240<!-- *********************************************************************** -->
1241
1242<div class="doc_text">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1243<p>
1244This section describes some of the advanced or obscure API's that most clients
1245do not need to be aware of. These API's tend manage the inner workings of the
1246LLVM system, and only need to be accessed in unusual circumstances.
1247</p>
1248</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1249
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1250<!-- ======================================================================= -->
1251<div class="doc_subsection">
1252 <a name="TypeResolve">LLVM Type Resolution</a>
1253</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1254
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1255<div class="doc_text">
1256
1257<p>
1258The LLVM type system has a very simple goal: allow clients to compare types for
1259structural equality with a simple pointer comparison (aka a shallow compare).
1260This goal makes clients much simpler and faster, and is used throughout the LLVM
1261system.
1262</p>
1263
1264<p>
1265Unfortunately achieving this goal is not a simple matter. In particular,
1266recursive types and late resolution of opaque types makes the situation very
1267difficult to handle. Fortunately, for the most part, our implementation makes
1268most clients able to be completely unaware of the nasty internal details. The
1269primary case where clients are exposed to the inner workings of it are when
1270building a recursive type. In addition to this case, the LLVM bytecode reader,
1271assembly parser, and linker also have to be aware of the inner workings of this
1272system.
1273</p>
1274
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1275<p>
1276For our purposes below, we need three concepts. First, an "Opaque Type" is
1277exactly as defined in the <a href="LangRef.html#t_opaque">language
1278reference</a>. Second an "Abstract Type" is any type which includes an
1279opaque type as part of its type graph (for example "<tt>{ opaque, int }</tt>").
1280Third, a concrete type is a type that is not an abstract type (e.g. "<tt>[ int,
1281float }</tt>").
1282</p>
1283
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1284</div>
1285
1286<!-- ______________________________________________________________________ -->
1287<div class="doc_subsubsection">
1288 <a name="BuildRecType">Basic Recursive Type Construction</a>
1289</div>
1290
1291<div class="doc_text">
1292
1293<p>
1294Because the most common question is "how do I build a recursive type with LLVM",
1295we answer it now and explain it as we go. Here we include enough to cause this
1296to be emitted to an output .ll file:
1297</p>
1298
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1299<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1300<pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1301%mylist = type { %mylist*, int }
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1302</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1303</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1304
1305<p>
1306To build this, use the following LLVM APIs:
1307</p>
1308
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1309<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1310<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1311// <i>Create the initial outer struct</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1312<a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
1313std::vector&lt;const Type*&gt; Elts;
1314Elts.push_back(PointerType::get(StructTy));
1315Elts.push_back(Type::IntTy);
1316StructType *NewSTy = StructType::get(Elts);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1317
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1318// <i>At this point, NewSTy = "{ opaque*, int }". Tell VMCore that</i>
1319// <i>the struct and the opaque type are actually the same.</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1320cast&lt;OpaqueType&gt;(StructTy.get())-&gt;<a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1321
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1322// <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1323// <i>kept up-to-date</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1324NewSTy = cast&lt;StructType&gt;(StructTy.get());
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1325
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1326// <i>Add a name for the type to the module symbol table (optional)</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1327MyModule-&gt;addTypeName("mylist", NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1328</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1329</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1330
1331<p>
1332This code shows the basic approach used to build recursive types: build a
1333non-recursive type using 'opaque', then use type unification to close the cycle.
1334The type unification step is performed by the <tt><a
1335ref="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
1336described next. After that, we describe the <a
1337href="#PATypeHolder">PATypeHolder class</a>.
1338</p>
1339
1340</div>
1341
1342<!-- ______________________________________________________________________ -->
1343<div class="doc_subsubsection">
1344 <a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
1345</div>
1346
1347<div class="doc_text">
1348<p>
1349The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
1350While this method is actually a member of the DerivedType class, it is most
1351often used on OpaqueType instances. Type unification is actually a recursive
1352process. After unification, types can become structurally isomorphic to
1353existing types, and all duplicates are deleted (to preserve pointer equality).
1354</p>
1355
1356<p>
1357In the example above, the OpaqueType object is definitely deleted.
1358Additionally, if there is an "{ \2*, int}" type already created in the system,
1359the pointer and struct type created are <b>also</b> deleted. Obviously whenever
1360a type is deleted, any "Type*" pointers in the program are invalidated. As
1361such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
1362live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
1363types can never move or be deleted). To deal with this, the <a
1364href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
1365reference to a possibly refined type, and the <a
1366href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
1367complex datastructures.
1368</p>
1369
1370</div>
1371
1372<!-- ______________________________________________________________________ -->
1373<div class="doc_subsubsection">
1374 <a name="PATypeHolder">The PATypeHolder Class</a>
1375</div>
1376
1377<div class="doc_text">
1378<p>
1379PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
1380happily goes about nuking types that become isomorphic to existing types, it
1381automatically updates all PATypeHolder objects to point to the new type. In the
1382example above, this allows the code to maintain a pointer to the resultant
1383resolved recursive type, even though the Type*'s are potentially invalidated.
1384</p>
1385
1386<p>
1387PATypeHolder is an extremely light-weight object that uses a lazy union-find
1388implementation to update pointers. For example the pointer from a Value to its
1389Type is maintained by PATypeHolder objects.
1390</p>
1391
1392</div>
1393
1394<!-- ______________________________________________________________________ -->
1395<div class="doc_subsubsection">
1396 <a name="AbstractTypeUser">The AbstractTypeUser Class</a>
1397</div>
1398
1399<div class="doc_text">
1400
1401<p>
1402Some data structures need more to perform more complex updates when types get
1403resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
1404move and potentially merge type planes in its representation when a pointer
1405changes.</p>
1406
1407<p>
1408To support this, a class can derive from the AbstractTypeUser class. This class
1409allows it to get callbacks when certain types are resolved. To register to get
1410callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1411methods can be called on a type. Note that these methods only work for <i>
1412abstract</i> types. Concrete types (those that do not include an opaque objects
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1413somewhere) can never be refined.
1414</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1415</div>
1416
1417
1418<!-- ======================================================================= -->
1419<div class="doc_subsection">
1420 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
1421</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1422
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1423<div class="doc_text">
1424<p>This class provides a symbol table that the <a
1425href="#Function"><tt>Function</tt></a> and <a href="#Module">
1426<tt>Module</tt></a> classes use for naming definitions. The symbol table can
1427provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
1428href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
1429type. It hides the data it contains and provides access to it through a
1430controlled interface.</p>
1431
1432<p>Note that the symbol table class is should not be directly accessed by most
1433clients. It should only be used when iteration over the symbol table names
1434themselves are required, which is very special purpose. Note that not all LLVM
1435<a href="#Value">Value</a>s have names, and those without names (i.e. they have
1436an empty name) do not exist in the symbol table.
1437</p>
1438
1439<p>To use the <tt>SymbolTable</tt> well, you need to understand the
1440structure of the information it holds. The class contains two
1441<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
1442<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
1443The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
1444are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
1445however, are stored in a single dimension and accessed only by name.</p>
1446
1447<p>The interface of this class provides three basic types of operations:
1448<ol>
1449 <li><em>Accessors</em>. Accessors provide read-only access to information
1450 such as finding a value for a name with the
1451 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1452 <li><em>Mutators</em>. Mutators allow the user to add information to the
1453 <tt>SymbolTable</tt> with methods like
1454 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1455 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1456 of the symbol table in well defined ways, such as the method
1457 <a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
1458</ol>
1459
1460<h3>Accessors</h3>
1461<dl>
1462 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
1463 </dt>
1464 <dd>The <tt>lookup</tt> method searches the type plane given by the
1465 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1466 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1467
1468 <dt><tt>Type* lookupType( const std::string&amp; name) const</tt>:</dt>
1469 <dd>The <tt>lookupType</tt> method searches through the types for a
1470 <tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
1471 is not found, null is returned.</dd>
1472
1473 <dt><tt>bool hasTypes() const</tt>:</dt>
1474 <dd>This function returns true if an entry has been made into the type
1475 map.</dd>
1476
1477 <dt><tt>bool isEmpty() const</tt>:</dt>
1478 <dd>This function returns true if both the value and types maps are
1479 empty</dd>
1480</dl>
1481
1482<h3>Mutators</h3>
1483<dl>
1484 <dt><tt>void insert(Value *Val)</tt>:</dt>
1485 <dd>This method adds the provided value to the symbol table. The Value must
1486 have both a name and a type which are extracted and used to place the value
1487 in the correct type plane under the value's name.</dd>
1488
1489 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1490 <dd> Inserts a constant or type into the symbol table with the specified
1491 name. There can be a many to one mapping between names and constants
1492 or types.</dd>
1493
1494 <dt><tt>void insert(const std::string&amp; Name, Type *Typ)</tt>:</dt>
1495 <dd> Inserts a type into the symbol table with the specified name. There
1496 can be a many-to-one mapping between names and types. This method
1497 allows a type with an existing entry in the symbol table to get
1498 a new name.</dd>
1499
1500 <dt><tt>void remove(Value* Val)</tt>:</dt>
1501 <dd> This method removes a named value from the symbol table. The
1502 type and name of the Value are extracted from \p N and used to
1503 lookup the Value in the correct type plane. If the Value is
1504 not in the symbol table, this method silently ignores the
1505 request.</dd>
1506
1507 <dt><tt>void remove(Type* Typ)</tt>:</dt>
1508 <dd> This method removes a named type from the symbol table. The
1509 name of the type is extracted from \P T and used to look up
1510 the Type in the type map. If the Type is not in the symbol
1511 table, this method silently ignores the request.</dd>
1512
1513 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1514 <dd> Remove a constant or type with the specified name from the
1515 symbol table.</dd>
1516
1517 <dt><tt>Type* remove(const std::string&amp; Name, Type* T)</tt>:</dt>
1518 <dd> Remove a type with the specified name from the symbol table.
1519 Returns the removed Type.</dd>
1520
1521 <dt><tt>Value *value_remove(const value_iterator&amp; It)</tt>:</dt>
1522 <dd> Removes a specific value from the symbol table.
1523 Returns the removed value.</dd>
1524
1525 <dt><tt>bool strip()</tt>:</dt>
1526 <dd> This method will strip the symbol table of its names leaving
1527 the type and values. </dd>
1528
1529 <dt><tt>void clear()</tt>:</dt>
1530 <dd>Empty the symbol table completely.</dd>
1531</dl>
1532
1533<h3>Iteration</h3>
1534<p>The following functions describe three types of iterators you can obtain
1535the beginning or end of the sequence for both const and non-const. It is
1536important to keep track of the different kinds of iterators. There are
1537three idioms worth pointing out:</p>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1538
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1539<table>
1540 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1541 <tr>
1542 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1543 <td align="left"><pre><tt>
1544for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1545 PE = ST.plane_end(); PI != PE; ++PI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1546 PI-&gt;first // <i>This is the Type* of the plane</i>
1547 PI-&gt;second // <i>This is the SymbolTable::ValueMap of name/Value pairs</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1548}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1549 </tt></pre></td>
1550 </tr>
1551 <tr>
1552 <td align="left">All name/Type Pairs</td><td>TI</td>
1553 <td align="left"><pre><tt>
1554for (SymbolTable::type_const_iterator TI = ST.type_begin(),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1555 TE = ST.type_end(); TI != TE; ++TI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1556 TI-&gt;first // <i>This is the name of the type</i>
1557 TI-&gt;second // <i>This is the Type* value associated with the name</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1558}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1559 </tt></pre></td>
1560 </tr>
1561 <tr>
1562 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1563 <td align="left"><pre><tt>
1564for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1565 VE = ST.value_end(SomeType); VI != VE; ++VI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1566 VI-&gt;first // <i>This is the name of the Value</i>
1567 VI-&gt;second // <i>This is the Value* value associated with the name</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1568}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1569 </tt></pre></td>
1570 </tr>
1571</table>
1572
1573<p>Using the recommended iterator names and idioms will help you avoid
1574making mistakes. Of particular note, make sure that whenever you use
1575value_begin(SomeType) that you always compare the resulting iterator
1576with value_end(SomeType) not value_end(SomeOtherType) or else you
1577will loop infinitely.</p>
1578
1579<dl>
1580
1581 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1582 <dd>Get an iterator that starts at the beginning of the type planes.
1583 The iterator will iterate over the Type/ValueMap pairs in the
1584 type planes. </dd>
1585
1586 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1587 <dd>Get a const_iterator that starts at the beginning of the type
1588 planes. The iterator will iterate over the Type/ValueMap pairs
1589 in the type planes. </dd>
1590
1591 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1592 <dd>Get an iterator at the end of the type planes. This serves as
1593 the marker for end of iteration over the type planes.</dd>
1594
1595 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1596 <dd>Get a const_iterator at the end of the type planes. This serves as
1597 the marker for end of iteration over the type planes.</dd>
1598
1599 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
1600 <dd>Get an iterator that starts at the beginning of a type plane.
1601 The iterator will iterate over the name/value pairs in the type plane.
1602 Note: The type plane must already exist before using this.</dd>
1603
1604 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
1605 <dd>Get a const_iterator that starts at the beginning of a type plane.
1606 The iterator will iterate over the name/value pairs in the type plane.
1607 Note: The type plane must already exist before using this.</dd>
1608
1609 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
1610 <dd>Get an iterator to the end of a type plane. This serves as the marker
1611 for end of iteration of the type plane.
1612 Note: The type plane must already exist before using this.</dd>
1613
1614 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
1615 <dd>Get a const_iterator to the end of a type plane. This serves as the
1616 marker for end of iteration of the type plane.
1617 Note: the type plane must already exist before using this.</dd>
1618
1619 <dt><tt>type_iterator type_begin()</tt>:</dt>
1620 <dd>Get an iterator to the start of the name/Type map.</dd>
1621
1622 <dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
1623 <dd> Get a const_iterator to the start of the name/Type map.</dd>
1624
1625 <dt><tt>type_iterator type_end()</tt>:</dt>
1626 <dd>Get an iterator to the end of the name/Type map. This serves as the
1627 marker for end of iteration of the types.</dd>
1628
1629 <dt><tt>type_const_iterator type_end() const</tt>:</dt>
1630 <dd>Get a const-iterator to the end of the name/Type map. This serves
1631 as the marker for end of iteration of the types.</dd>
1632
1633 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
1634 <dd>This method returns a plane_const_iterator for iteration over
1635 the type planes starting at a specific plane, given by \p Ty.</dd>
1636
1637 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
1638 <dd>This method returns a plane_iterator for iteration over the
1639 type planes starting at a specific plane, given by \p Ty.</dd>
1640
1641</dl>
1642</div>
1643
1644
1645
1646<!-- *********************************************************************** -->
1647<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1648 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
1649</div>
1650<!-- *********************************************************************** -->
1651
1652<div class="doc_text">
1653
1654<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1655being inspected or transformed. The core LLVM classes are defined in
1656header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1657the <tt>lib/VMCore</tt> directory.</p>
1658
1659</div>
1660
1661<!-- ======================================================================= -->
1662<div class="doc_subsection">
1663 <a name="Value">The <tt>Value</tt> class</a>
1664</div>
1665
1666<div>
1667
1668<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
1669<br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1670doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1671
1672<p>The <tt>Value</tt> class is the most important class in the LLVM Source
1673base. It represents a typed value that may be used (among other things) as an
1674operand to an instruction. There are many different types of <tt>Value</tt>s,
1675such as <a href="#Constant"><tt>Constant</tt></a>s,<a
1676href="#Argument"><tt>Argument</tt></a>s. Even <a
1677href="#Instruction"><tt>Instruction</tt></a>s and <a
1678href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
1679
1680<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
1681for a program. For example, an incoming argument to a function (represented
1682with an instance of the <a href="#Argument">Argument</a> class) is "used" by
1683every instruction in the function that references the argument. To keep track
1684of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
1685href="#User"><tt>User</tt></a>s that is using it (the <a
1686href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
1687graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
1688def-use information in the program, and is accessible through the <tt>use_</tt>*
1689methods, shown below.</p>
1690
1691<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
1692and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
1693method. In addition, all LLVM values can be named. The "name" of the
1694<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
1695
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1696<div class="doc_code">
1697<pre>
1698%<b>foo</b> = add int 1, 2
1699</pre>
1700</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1701
1702<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
1703that the name of any value may be missing (an empty string), so names should
1704<b>ONLY</b> be used for debugging (making the source code easier to read,
1705debugging printouts), they should not be used to keep track of values or map
1706between them. For this purpose, use a <tt>std::map</tt> of pointers to the
1707<tt>Value</tt> itself instead.</p>
1708
1709<p>One important aspect of LLVM is that there is no distinction between an SSA
1710variable and the operation that produces it. Because of this, any reference to
1711the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]1712argument, for example) is represented as a direct pointer to the instance of
1713the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1714represents this value. Although this may take some getting used to, it
1715simplifies the representation and makes it easier to manipulate.</p>
1716
1717</div>
1718
1719<!-- _______________________________________________________________________ -->
1720<div class="doc_subsubsection">
1721 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
1722</div>
1723
1724<div class="doc_text">
1725
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1726<ul>
1727 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
1728use-list<br>
1729 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
1730the use-list<br>
1731 <tt>unsigned use_size()</tt> - Returns the number of users of the
1732value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1733 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1734 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
1735the use-list.<br>
1736 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
1737use-list.<br>
1738 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
1739element in the list.
1740 <p> These methods are the interface to access the def-use
1741information in LLVM. As with all other iterators in LLVM, the naming
1742conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1743 </li>
1744 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1745 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1746 </li>
1747 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1748 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1749 <tt>void setName(const std::string &amp;Name)</tt>
1750 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
1751be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1752 </li>
1753 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1754
1755 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
1756 href="#User"><tt>User</tt>s</a> of the current value to refer to
1757 "<tt>V</tt>" instead. For example, if you detect that an instruction always
1758 produces a constant value (for example through constant folding), you can
1759 replace all uses of the instruction with the constant like this:</p>
1760
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1761<div class="doc_code">
1762<pre>
1763Inst-&gt;replaceAllUsesWith(ConstVal);
1764</pre>
1765</div>
1766
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1767</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1768
1769</div>
1770
1771<!-- ======================================================================= -->
1772<div class="doc_subsection">
1773 <a name="User">The <tt>User</tt> class</a>
1774</div>
1775
1776<div class="doc_text">
1777
1778<p>
1779<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]1780doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1781Superclass: <a href="#Value"><tt>Value</tt></a></p>
1782
1783<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
1784refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1785that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1786referring to. The <tt>User</tt> class itself is a subclass of
1787<tt>Value</tt>.</p>
1788
1789<p>The operands of a <tt>User</tt> point directly to the LLVM <a
1790href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1791Single Assignment (SSA) form, there can only be one definition referred to,
1792allowing this direct connection. This connection provides the use-def
1793information in LLVM.</p>
1794
1795</div>
1796
1797<!-- _______________________________________________________________________ -->
1798<div class="doc_subsubsection">
1799 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
1800</div>
1801
1802<div class="doc_text">
1803
1804<p>The <tt>User</tt> class exposes the operand list in two ways: through
1805an index access interface and through an iterator based interface.</p>
1806
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1807<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1808 <li><tt>Value *getOperand(unsigned i)</tt><br>
1809 <tt>unsigned getNumOperands()</tt>
1810 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1811convenient form for direct access.</p></li>
1812
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1813 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
1814list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1815 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
1816the operand list.<br>
1817 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1818operand list.
1819 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1820the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1821</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1822
1823</div>
1824
1825<!-- ======================================================================= -->
1826<div class="doc_subsection">
1827 <a name="Instruction">The <tt>Instruction</tt> class</a>
1828</div>
1829
1830<div class="doc_text">
1831
1832<p><tt>#include "</tt><tt><a
1833href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1834doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1835Superclasses: <a href="#User"><tt>User</tt></a>, <a
1836href="#Value"><tt>Value</tt></a></p>
1837
1838<p>The <tt>Instruction</tt> class is the common base class for all LLVM
1839instructions. It provides only a few methods, but is a very commonly used
1840class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1841opcode (instruction type) and the parent <a
1842href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1843into. To represent a specific type of instruction, one of many subclasses of
1844<tt>Instruction</tt> are used.</p>
1845
1846<p> Because the <tt>Instruction</tt> class subclasses the <a
1847href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1848way as for other <a href="#User"><tt>User</tt></a>s (with the
1849<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1850<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
1851the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
1852file contains some meta-data about the various different types of instructions
1853in LLVM. It describes the enum values that are used as opcodes (for example
1854<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
1855concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
1856example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1857href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1858this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1859<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1860
1861</div>
1862
1863<!-- _______________________________________________________________________ -->
1864<div class="doc_subsubsection">
1865 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
1866 class</a>
1867</div>
1868
1869<div class="doc_text">
1870
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1871<ul>
1872 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1873 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
1874this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1875 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1876 <p>Returns true if the instruction writes to memory, i.e. it is a
1877 <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]1878 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1879 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1880 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1881 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1882in all ways to the original except that the instruction has no parent
1883(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1884and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1885</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1886
1887</div>
1888
1889<!-- ======================================================================= -->
1890<div class="doc_subsection">
1891 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1892</div>
1893
1894<div class="doc_text">
1895
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1896<p><tt>#include "<a
1897href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
1898doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
1899Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1900Superclass: <a href="#Value"><tt>Value</tt></a></p>
1901
1902<p>This class represents a single entry multiple exit section of the code,
1903commonly known as a basic block by the compiler community. The
1904<tt>BasicBlock</tt> class maintains a list of <a
1905href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
1906Matching the language definition, the last element of this list of instructions
1907is always a terminator instruction (a subclass of the <a
1908href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
1909
1910<p>In addition to tracking the list of instructions that make up the block, the
1911<tt>BasicBlock</tt> class also keeps track of the <a
1912href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
1913
1914<p>Note that <tt>BasicBlock</tt>s themselves are <a
1915href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1916like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1917<tt>label</tt>.</p>
1918
1919</div>
1920
1921<!-- _______________________________________________________________________ -->
1922<div class="doc_subsubsection">
1923 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
1924 class</a>
1925</div>
1926
1927<div class="doc_text">
1928
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1929<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1930
1931<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1932 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1933
1934<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1935insertion into a function. The constructor optionally takes a name for the new
1936block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
1937the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
1938automatically inserted at the end of the specified <a
1939href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1940manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
1941
1942<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1943<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1944<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1945<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1946STL-style functions for accessing the instruction list.
1947
1948<p>These methods and typedefs are forwarding functions that have the same
1949semantics as the standard library methods of the same names. These methods
1950expose the underlying instruction list of a basic block in a way that is easy to
1951manipulate. To get the full complement of container operations (including
1952operations to update the list), you must use the <tt>getInstList()</tt>
1953method.</p></li>
1954
1955<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
1956
1957<p>This method is used to get access to the underlying container that actually
1958holds the Instructions. This method must be used when there isn't a forwarding
1959function in the <tt>BasicBlock</tt> class for the operation that you would like
1960to perform. Because there are no forwarding functions for "updating"
1961operations, you need to use this if you want to update the contents of a
1962<tt>BasicBlock</tt>.</p></li>
1963
1964<li><tt><a href="#Function">Function</a> *getParent()</tt>
1965
1966<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1967embedded into, or a null pointer if it is homeless.</p></li>
1968
1969<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
1970
1971<p> Returns a pointer to the terminator instruction that appears at the end of
1972the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1973instruction in the block is not a terminator, then a null pointer is
1974returned.</p></li>
1975
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1976</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1977
1978</div>
1979
1980<!-- ======================================================================= -->
1981<div class="doc_subsection">
1982 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1983</div>
1984
1985<div class="doc_text">
1986
1987<p><tt>#include "<a
1988href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1989doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
1990Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]1991Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
1992<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]1993
1994<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1995href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1996visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1997Because they are visible at global scope, they are also subject to linking with
1998other globals defined in different translation units. To control the linking
1999process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
2000<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2001defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2002
2003<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
2004<tt>static</tt> in C), it is not visible to code outside the current translation
2005unit, and does not participate in linking. If it has external linkage, it is
2006visible to external code, and does participate in linking. In addition to
2007linkage information, <tt>GlobalValue</tt>s keep track of which <a
2008href="#Module"><tt>Module</tt></a> they are currently part of.</p>
2009
2010<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
2011by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
2012global is always a pointer to its contents. It is important to remember this
2013when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
2014be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
2015subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
2016int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
2017the address of the first element of this array and the value of the
2018<tt>GlobalVariable</tt> are the same, they have different types. The
2019<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
2020is <tt>int.</tt> Because of this, accessing a global value requires you to
2021dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
2022can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
2023Language Reference Manual</a>.</p>
2024
2025</div>
2026
2027<!-- _______________________________________________________________________ -->
2028<div class="doc_subsubsection">
2029 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
2030 class</a>
2031</div>
2032
2033<div class="doc_text">
2034
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2035<ul>
2036 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2037 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2038 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
2039 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
2040 <p> </p>
2041 </li>
2042 <li><tt><a href="#Module">Module</a> *getParent()</tt>
2043 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2044GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2045</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2046
2047</div>
2048
2049<!-- ======================================================================= -->
2050<div class="doc_subsection">
2051 <a name="Function">The <tt>Function</tt> class</a>
2052</div>
2053
2054<div class="doc_text">
2055
2056<p><tt>#include "<a
2057href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2058info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2059Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2060<a href="#Constant"><tt>Constant</tt></a>,
2061<a href="#User"><tt>User</tt></a>,
2062<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2063
2064<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
2065actually one of the more complex classes in the LLVM heirarchy because it must
2066keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2067of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
2068<a href="#Argument"><tt>Argument</tt></a>s, and a
2069<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2070
2071<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
2072commonly used part of <tt>Function</tt> objects. The list imposes an implicit
2073ordering of the blocks in the function, which indicate how the code will be
2074layed out by the backend. Additionally, the first <a
2075href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
2076<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
2077block. There are no implicit exit nodes, and in fact there may be multiple exit
2078nodes from a single <tt>Function</tt>. If the <a
2079href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
2080the <tt>Function</tt> is actually a function declaration: the actual body of the
2081function hasn't been linked in yet.</p>
2082
2083<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
2084<tt>Function</tt> class also keeps track of the list of formal <a
2085href="#Argument"><tt>Argument</tt></a>s that the function receives. This
2086container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
2087nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
2088the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
2089
2090<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
2091LLVM feature that is only used when you have to look up a value by name. Aside
2092from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
2093internally to make sure that there are not conflicts between the names of <a
2094href="#Instruction"><tt>Instruction</tt></a>s, <a
2095href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
2096href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
2097
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2098<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
2099and therefore also a <a href="#Constant">Constant</a>. The value of the function
2100is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2101</div>
2102
2103<!-- _______________________________________________________________________ -->
2104<div class="doc_subsubsection">
2105 <a name="m_Function">Important Public Members of the <tt>Function</tt>
2106 class</a>
2107</div>
2108
2109<div class="doc_text">
2110
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2111<ul>
2112 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2113 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2114
2115 <p>Constructor used when you need to create new <tt>Function</tt>s to add
2116 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2117 create and what type of linkage the function should have. The <a
2118 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2119 specifies the formal arguments and return value for the function. The same
2120 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
2121 create multiple functions. The <tt>Parent</tt> argument specifies the Module
2122 in which the function is defined. If this argument is provided, the function
2123 will automatically be inserted into that module's list of
2124 functions.</p></li>
2125
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2126 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2127
2128 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
2129 function is "external", it does not have a body, and thus must be resolved
2130 by linking with a function defined in a different translation unit.</p></li>
2131
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2132 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2133 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2134
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2135 <tt>begin()</tt>, <tt>end()</tt>
2136 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2137
2138 <p>These are forwarding methods that make it easy to access the contents of
2139 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
2140 list.</p></li>
2141
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2142 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2143
2144 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
2145 is necessary to use when you need to update the list or perform a complex
2146 action that doesn't have a forwarding method.</p></li>
2147
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2148 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2149iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2150 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2151
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2152 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2153 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2154
2155 <p>These are forwarding methods that make it easy to access the contents of
2156 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
2157 list.</p></li>
2158
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2159 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2160
2161 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
2162 necessary to use when you need to update the list or perform a complex
2163 action that doesn't have a forwarding method.</p></li>
2164
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2165 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2166
2167 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
2168 function. Because the entry block for the function is always the first
2169 block, this returns the first block of the <tt>Function</tt>.</p></li>
2170
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2171 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
2172 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2173
2174 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
2175 <tt>Function</tt> and returns the return type of the function, or the <a
2176 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
2177 function.</p></li>
2178
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2179 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2180
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2181 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2182 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2183</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2184
2185</div>
2186
2187<!-- ======================================================================= -->
2188<div class="doc_subsection">
2189 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
2190</div>
2191
2192<div class="doc_text">
2193
2194<p><tt>#include "<a
2195href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
2196<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2197doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2198 Class</a><br>
2199Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2200<a href="#Constant"><tt>Constant</tt></a>,
2201<a href="#User"><tt>User</tt></a>,
2202<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2203
2204<p>Global variables are represented with the (suprise suprise)
2205<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
2206subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
2207always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2208"name" refers to their constant address). See
2209<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
2210variables may have an initial value (which must be a
2211<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
2212they may be marked as "constant" themselves (indicating that their contents
2213never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2214</div>
2215
2216<!-- _______________________________________________________________________ -->
2217<div class="doc_subsubsection">
2218 <a name="m_GlobalVariable">Important Public Members of the
2219 <tt>GlobalVariable</tt> class</a>
2220</div>
2221
2222<div class="doc_text">
2223
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2224<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2225 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
2226 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
2227 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
2228
2229 <p>Create a new global variable of the specified type. If
2230 <tt>isConstant</tt> is true then the global variable will be marked as
2231 unchanging for the program. The Linkage parameter specifies the type of
2232 linkage (internal, external, weak, linkonce, appending) for the variable. If
2233 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
2234 the resultant global variable will have internal linkage. AppendingLinkage
2235 concatenates together all instances (in different translation units) of the
2236 variable into a single variable but is only applicable to arrays. &nbsp;See
2237 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
2238 further details on linkage types. Optionally an initializer, a name, and the
2239 module to put the variable into may be specified for the global variable as
2240 well.</p></li>
2241
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2242 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2243
2244 <p>Returns true if this is a global variable that is known not to
2245 be modified at runtime.</p></li>
2246
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2247 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2248
2249 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
2250
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2251 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2252
2253 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
2254 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2255</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2256
2257</div>
2258
2259<!-- ======================================================================= -->
2260<div class="doc_subsection">
2261 <a name="Module">The <tt>Module</tt> class</a>
2262</div>
2263
2264<div class="doc_text">
2265
2266<p><tt>#include "<a
2267href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2268<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2269
2270<p>The <tt>Module</tt> class represents the top level structure present in LLVM
2271programs. An LLVM module is effectively either a translation unit of the
2272original program or a combination of several translation units merged by the
2273linker. The <tt>Module</tt> class keeps track of a list of <a
2274href="#Function"><tt>Function</tt></a>s, a list of <a
2275href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
2276href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
2277helpful member functions that try to make common operations easy.</p>
2278
2279</div>
2280
2281<!-- _______________________________________________________________________ -->
2282<div class="doc_subsubsection">
2283 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
2284</div>
2285
2286<div class="doc_text">
2287
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2288<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2289 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2290</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2291
2292<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
2293provide a name for it (probably based on the name of the translation unit).</p>
2294
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2295<ul>
2296 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]2297 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2298
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2299 <tt>begin()</tt>, <tt>end()</tt>
2300 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2301
2302 <p>These are forwarding methods that make it easy to access the contents of
2303 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
2304 list.</p></li>
2305
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2306 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2307
2308 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
2309 necessary to use when you need to update the list or perform a complex
2310 action that doesn't have a forwarding method.</p>
2311
2312 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2313</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2314
2315<hr>
2316
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2317<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2318 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2319
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2320 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2321
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2322 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2323 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2324
2325 <p> These are forwarding methods that make it easy to access the contents of
2326 a <tt>Module</tt> object's <a
2327 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
2328
2329 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
2330
2331 <p>Returns the list of <a
2332 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2333 use when you need to update the list or perform a complex action that
2334 doesn't have a forwarding method.</p>
2335
2336 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2337</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2338
2339<hr>
2340
2341<ul>
2342 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2343
2344 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2345 for this <tt>Module</tt>.</p>
2346
2347 <p><!-- Convenience methods --></p></li>
2348</ul>
2349
2350<hr>
2351
2352<ul>
2353 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2354 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2355
2356 <p>Look up the specified function in the <tt>Module</tt> <a
2357 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2358 <tt>null</tt>.</p></li>
2359
2360 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2361 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2362
2363 <p>Look up the specified function in the <tt>Module</tt> <a
2364 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2365 external declaration for the function and return it.</p></li>
2366
2367 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2368
2369 <p>If there is at least one entry in the <a
2370 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2371 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2372 string.</p></li>
2373
2374 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
2375 href="#Type">Type</a> *Ty)</tt>
2376
2377 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2378 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2379 name, true is returned and the <a
2380 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2381</ul>
2382
2383</div>
2384
2385<!-- ======================================================================= -->
2386<div class="doc_subsection">
2387 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2388</div>
2389
2390<div class="doc_text">
2391
2392<p>Constant represents a base class for different types of constants. It
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame^]2393is subclassed by ConstantBool, ConstantInt, ConstantArray etc for representing
2394the various types of Constants.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2395
2396</div>
2397
2398<!-- _______________________________________________________________________ -->
2399<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2400 <a name="m_Constant">Important Public Methods</a>
2401</div>
2402<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2403</div>
2404
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2405<!-- _______________________________________________________________________ -->
2406<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2407<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2408<ul>
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame^]2409 <li>ConstantInt : This subclass of Constant represents an integer constant.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2410 <ul>
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame^]2411 <li><tt>int64_t getSExtValue() const</tt>: Returns the underlying value of
2412 this constant as a sign extended signed integer value.</li>
2413 <li><tt>uint64_t getZExtValue() const</tt>: Returns the underlying value
2414 of this constant as a zero extended unsigned integer value.</li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2415 </ul>
2416 </li>
2417 <li>ConstantFP : This class represents a floating point constant.
2418 <ul>
2419 <li><tt>double getValue() const</tt>: Returns the underlying value of
2420 this constant. </li>
2421 </ul>
2422 </li>
2423 <li>ConstantBool : This represents a boolean constant.
2424 <ul>
2425 <li><tt>bool getValue() const</tt>: Returns the underlying value of this
2426 constant. </li>
2427 </ul>
2428 </li>
2429 <li>ConstantArray : This represents a constant array.
2430 <ul>
2431 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2432 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2433 </ul>
2434 </li>
2435 <li>ConstantStruct : This represents a constant struct.
2436 <ul>
2437 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2438 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2439 </ul>
2440 </li>
2441 <li>GlobalValue : This represents either a global variable or a function. In
2442 either case, the value is a constant fixed address (after linking).
2443 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2444</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2445</div>
2446
2447<!-- ======================================================================= -->
2448<div class="doc_subsection">
2449 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
2450</div>
2451
2452<div class="doc_text">
2453
2454<p>Type as noted earlier is also a subclass of a Value class. Any primitive
2455type (like int, short etc) in LLVM is an instance of Type Class. All other
2456types are instances of subclasses of type like FunctionType, ArrayType
2457etc. DerivedType is the interface for all such dervied types including
2458FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
2459be recursive (StructType). There exists exactly one instance of any type
2460structure at a time. This allows using pointer equality of Type *s for comparing
2461types.</p>
2462
2463</div>
2464
2465<!-- _______________________________________________________________________ -->
2466<div class="doc_subsubsection">
2467 <a name="m_Value">Important Public Methods</a>
2468</div>
2469
2470<div class="doc_text">
2471
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2472<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2473
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2474 <li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
2475 is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
2476 not true for Float and Double. </li>
2477
2478 <li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
2479 unsigned. This is not quite the complement of isSigned... nonnumeric types
2480 return false as they do with isSigned. This returns true for UByteTy,
2481 UShortTy, UIntTy, and ULongTy. </li>
2482
Chris Lattner4573f1b2004-07-08 17:49:37 +0000[diff] [blame]2483 <li><tt>bool isInteger() const</tt>: Equivalent to isSigned() || isUnsigned().</li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2484
2485 <li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
2486 type, which is either Bool type or one of the Integer types.</li>
2487
2488 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
2489 floating point types.</li>
2490
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2491 <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
2492 this type can be converted to 'Ty' without any reinterpretation of bits. For
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2493 example, uint to int or one pointer type to another.</li>
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2494</ul>
2495</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2496
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2497<!-- _______________________________________________________________________ -->
2498<div class="doc_subsubsection">
2499 <a name="m_Value">Important Derived Types</a>
2500</div>
2501<div class="doc_text">
2502<ul>
2503 <li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2504 <ul>
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2505 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2506 of the elements in the sequential type. </li>
2507 </ul>
2508 </li>
2509 <li>ArrayType : This is a subclass of SequentialType and defines interface for
2510 array types.
2511 <ul>
2512 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2513 elements in the array. </li>
2514 </ul>
2515 </li>
2516 <li>PointerType : Subclass of SequentialType for pointer types. </li>
2517 <li>StructType : subclass of DerivedTypes for struct types </li>
2518 <li>FunctionType : subclass of DerivedTypes for function types.
2519 <ul>
2520 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2521 function</li>
2522 <li><tt> const Type * getReturnType() const</tt>: Returns the
2523 return type of the function.</li>
2524 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2525 the type of the ith parameter.</li>
2526 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2527 number of formal parameters.</li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2528 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2529 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2530</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2531</div>
2532
2533<!-- ======================================================================= -->
2534<div class="doc_subsection">
2535 <a name="Argument">The <tt>Argument</tt> class</a>
2536</div>
2537
2538<div class="doc_text">
2539
2540<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2541arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2542arguments. An argument has a pointer to the parent Function.</p>
2543
2544</div>
2545
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2546<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2547<hr>
2548<address>
2549 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
2550 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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2552 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
2553
2554 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2555 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2556 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2557 Last modified: $Date$
2558</address>
2559
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2560</body>
2561</html>