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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>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]38 <li><a href="#Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]39option</a></li>
40<!--
41 <li>The <tt>InstVisitor</tt> template
42 <li>The general graph API
43-->
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]44 <li><a href="#ViewGraph">Viewing graphs while debugging code</a></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]45 </ul>
46 </li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]47 <li><a href="#datastructure">Picking the Right Data Structure for a Task</a>
48 <ul>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]49 <li><a href="#ds_sequential">Sequential Containers (std::vector, std::list, etc)</a>
50 <ul>
51 <li><a href="#dss_fixedarrays">Fixed Size Arrays</a></li>
52 <li><a href="#dss_heaparrays">Heap Allocated Arrays</a></li>
53 <li><a href="#dss_smallvector">"llvm/ADT/SmallVector.h"</a></li>
54 <li><a href="#dss_vector">&lt;vector&gt;</a></li>
55 <li><a href="#dss_deque">&lt;deque&gt;</a></li>
56 <li><a href="#dss_list">&lt;list&gt;</a></li>
57 <li><a href="#dss_ilist">llvm/ADT/ilist</a></li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]58 </ul></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]59 <li><a href="#ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
60 <ul>
61 <li><a href="#dss_sortedvectorset">A sorted 'vector'</a></li>
62 <li><a href="#dss_smallset">"llvm/ADT/SmallSet.h"</a></li>
63 <li><a href="#dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a></li>
64 <li><a href="#dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a></li>
65 <li><a href="#dss_set">&lt;set&gt;</a></li>
66 <li><a href="#dss_setvector">"llvm/ADT/SetVector.h"</a></li>
67 <li><a href="#dss_otherset">Other Options</a></li>
68 </ul></li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]69 <li><a href="#ds_map">Map-Like Containers (std::map, DenseMap, etc)</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]70 </ul>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]71 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]72 <li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]73 <ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]74 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
75 <ul>
76 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
77in a <tt>Function</tt></a> </li>
78 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
79in a <tt>BasicBlock</tt></a> </li>
80 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
81in a <tt>Function</tt></a> </li>
82 <li><a href="#iterate_convert">Turning an iterator into a
83class pointer</a> </li>
84 <li><a href="#iterate_complex">Finding call sites: a more
85complex example</a> </li>
86 <li><a href="#calls_and_invokes">Treating calls and invokes
87the same way</a> </li>
88 <li><a href="#iterate_chains">Iterating over def-use &amp;
89use-def chains</a> </li>
90 </ul>
91 </li>
92 <li><a href="#simplechanges">Making simple changes</a>
93 <ul>
94 <li><a href="#schanges_creating">Creating and inserting new
95 <tt>Instruction</tt>s</a> </li>
96 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
97 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
98with another <tt>Value</tt></a> </li>
99 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]100 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]101<!--
102 <li>Working with the Control Flow Graph
103 <ul>
104 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
105 <li>
106 <li>
107 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]108-->
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]109 </ul>
110 </li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]111
112 <li><a href="#advanced">Advanced Topics</a>
113 <ul>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]114 <li><a href="#TypeResolve">LLVM Type Resolution</a>
115 <ul>
116 <li><a href="#BuildRecType">Basic Recursive Type Construction</a></li>
117 <li><a href="#refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a></li>
118 <li><a href="#PATypeHolder">The PATypeHolder Class</a></li>
119 <li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
120 </ul></li>
121
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]122 <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
123 </ul></li>
124
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]125 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]126 <ul>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]127 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]128 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]129 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]130 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]131 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]132 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
133 <ul>
134 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
135 </ul>
136 </li>
137 <li><a href="#Module">The <tt>Module</tt> class</a></li>
138 <li><a href="#Constant">The <tt>Constant</tt> class</a>
139 <ul>
140 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
141 <ul>
142 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
143 <li><a href="#Function">The <tt>Function</tt> class</a></li>
144 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
145 </ul>
146 </li>
147 </ul>
148 </li>
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]149 </ul>
150 </li>
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]151 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]152 </ul>
153 </li>
154 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]155 </li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]156</ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]157
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]158<div class="doc_author">
159 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner94c43592004-05-26 16:52:55 +0000[diff] [blame]160 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
161 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
162 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]163</div>
164
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]165<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]166<div class="doc_section">
167 <a name="introduction">Introduction </a>
168</div>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]169<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]170
171<div class="doc_text">
172
173<p>This document is meant to highlight some of the important classes and
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]174interfaces available in the LLVM source-base. This manual is not
175intended to explain what LLVM is, how it works, and what LLVM code looks
176like. It assumes that you know the basics of LLVM and are interested
177in writing transformations or otherwise analyzing or manipulating the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]178code.</p>
179
180<p>This document should get you oriented so that you can find your
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]181way in the continuously growing source code that makes up the LLVM
182infrastructure. Note that this manual is not intended to serve as a
183replacement for reading the source code, so if you think there should be
184a method in one of these classes to do something, but it's not listed,
185check the source. Links to the <a href="/doxygen/">doxygen</a> sources
186are provided to make this as easy as possible.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]187
188<p>The first section of this document describes general information that is
189useful to know when working in the LLVM infrastructure, and the second describes
190the Core LLVM classes. In the future this manual will be extended with
191information describing how to use extension libraries, such as dominator
192information, CFG traversal routines, and useful utilities like the <tt><a
193href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
194
195</div>
196
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]197<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]198<div class="doc_section">
199 <a name="general">General Information</a>
200</div>
201<!-- *********************************************************************** -->
202
203<div class="doc_text">
204
205<p>This section contains general information that is useful if you are working
206in the LLVM source-base, but that isn't specific to any particular API.</p>
207
208</div>
209
210<!-- ======================================================================= -->
211<div class="doc_subsection">
212 <a name="stl">The C++ Standard Template Library</a>
213</div>
214
215<div class="doc_text">
216
217<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]218perhaps much more than you are used to, or have seen before. Because of
219this, you might want to do a little background reading in the
220techniques used and capabilities of the library. There are many good
221pages that discuss the STL, and several books on the subject that you
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]222can get, so it will not be discussed in this document.</p>
223
224<p>Here are some useful links:</p>
225
226<ol>
227
228<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
229reference</a> - an excellent reference for the STL and other parts of the
230standard C++ library.</li>
231
232<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]233O'Reilly book in the making. It has a decent
234Standard Library
235Reference 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]236published.</li>
237
238<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
239Questions</a></li>
240
241<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
242Contains a useful <a
243href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
244STL</a>.</li>
245
246<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
247Page</a></li>
248
Tanya Lattner79445ba2004-12-08 18:34:56 +0000[diff] [blame]249<li><a href="http://64.78.49.204/">
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]250Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
251the book).</a></li>
252
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]253</ol>
254
255<p>You are also encouraged to take a look at the <a
256href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
257to write maintainable code more than where to put your curly braces.</p>
258
259</div>
260
261<!-- ======================================================================= -->
262<div class="doc_subsection">
263 <a name="stl">Other useful references</a>
264</div>
265
266<div class="doc_text">
267
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]268<ol>
269<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]270Branch and Tag Primer</a></li>
Misha Brukmana0f71e42004-06-18 18:39:00 +0000[diff] [blame]271<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
272static and shared libraries across platforms</a></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]273</ol>
274
275</div>
276
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]277<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]278<div class="doc_section">
279 <a name="apis">Important and useful LLVM APIs</a>
280</div>
281<!-- *********************************************************************** -->
282
283<div class="doc_text">
284
285<p>Here we highlight some LLVM APIs that are generally useful and good to
286know about when writing transformations.</p>
287
288</div>
289
290<!-- ======================================================================= -->
291<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]292 <a name="isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt> and
293 <tt>dyn_cast&lt;&gt;</tt> templates</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]294</div>
295
296<div class="doc_text">
297
298<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]299These templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
300operator, but they don't have some drawbacks (primarily stemming from
301the fact that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that
302have a v-table). Because they are used so often, you must know what they
303do and how they work. All of these templates are defined in the <a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]304 href="/doxygen/Casting_8h-source.html"><tt>llvm/Support/Casting.h</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]305file (note that you very rarely have to include this file directly).</p>
306
307<dl>
308 <dt><tt>isa&lt;&gt;</tt>: </dt>
309
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]310 <dd><p>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]311 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
312 a reference or pointer points to an instance of the specified class. This can
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]313 be very useful for constraint checking of various sorts (example below).</p>
314 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]315
316 <dt><tt>cast&lt;&gt;</tt>: </dt>
317
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]318 <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]319 converts a pointer or reference from a base class to a derived cast, causing
320 an assertion failure if it is not really an instance of the right type. This
321 should be used in cases where you have some information that makes you believe
322 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]323 and <tt>cast&lt;&gt;</tt> template is:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]324
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]325<div class="doc_code">
326<pre>
327static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
328 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))
329 return true;
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]330
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]331 // <i>Otherwise, it must be an instruction...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]332 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
333}
334</pre>
335</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]336
337 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
338 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
339 operator.</p>
340
341 </dd>
342
343 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
344
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]345 <dd><p>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation.
346 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]347 pointer to it (this operator does not work with references). If the operand is
348 not of the correct type, a null pointer is returned. Thus, this works very
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]349 much like the <tt>dynamic_cast&lt;&gt;</tt> operator in C++, and should be
350 used in the same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt>
351 operator is used in an <tt>if</tt> statement or some other flow control
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]352 statement like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]353
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]354<div class="doc_code">
355<pre>
356if (<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]357 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]358}
359</pre>
360</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]361
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]362 <p>This form of the <tt>if</tt> statement effectively combines together a call
363 to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
364 statement, which is very convenient.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]365
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]366 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
367 <tt>dynamic_cast&lt;&gt;</tt> or Java's <tt>instanceof</tt> operator, can be
368 abused. In particular, you should not use big chained <tt>if/then/else</tt>
369 blocks to check for lots of different variants of classes. If you find
370 yourself wanting to do this, it is much cleaner and more efficient to use the
371 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]372
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]373 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]374
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]375 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
376
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]377 <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]378 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as an
379 argument (which it then propagates). This can sometimes be useful, allowing
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]380 you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]381
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]382 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]383
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]384 <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]385 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
386 as an argument (which it then propagates). This can sometimes be useful,
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]387 allowing you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]388
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]389</dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]390
391<p>These five templates can be used with any classes, whether they have a
392v-table or not. To add support for these templates, you simply need to add
393<tt>classof</tt> static methods to the class you are interested casting
394to. Describing this is currently outside the scope of this document, but there
395are lots of examples in the LLVM source base.</p>
396
397</div>
398
399<!-- ======================================================================= -->
400<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]401 <a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]402</div>
403
404<div class="doc_text">
405
406<p>Often when working on your pass you will put a bunch of debugging printouts
407and other code into your pass. After you get it working, you want to remove
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]408it, 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]409across).</p>
410
411<p> Naturally, because of this, you don't want to delete the debug printouts,
412but you don't want them to always be noisy. A standard compromise is to comment
413them out, allowing you to enable them if you need them in the future.</p>
414
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]415<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]416file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
417this problem. Basically, you can put arbitrary code into the argument of the
418<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
419tool) is run with the '<tt>-debug</tt>' command line argument:</p>
420
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]421<div class="doc_code">
422<pre>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]423DOUT &lt;&lt; "I am here!\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]424</pre>
425</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]426
427<p>Then you can run your pass like this:</p>
428
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]429<div class="doc_code">
430<pre>
431$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]432<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]433$ opt &lt; a.bc &gt; /dev/null -mypass -debug
434I am here!
435</pre>
436</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]437
438<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
439to not have to create "yet another" command line option for the debug output for
440your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
441so they do not cause a performance impact at all (for the same reason, they
442should also not contain side-effects!).</p>
443
444<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
445enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
446"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
447program hasn't been started yet, you can always just run it with
448<tt>-debug</tt>.</p>
449
450</div>
451
452<!-- _______________________________________________________________________ -->
453<div class="doc_subsubsection">
Chris Lattnerc9151082005-04-26 22:57:07 +0000[diff] [blame]454 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]455 the <tt>-debug-only</tt> option</a>
456</div>
457
458<div class="doc_text">
459
460<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
461just turns on <b>too much</b> information (such as when working on the code
462generator). If you want to enable debug information with more fine-grained
463control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
464option as follows:</p>
465
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]466<div class="doc_code">
467<pre>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]468DOUT &lt;&lt; "No debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]469#undef DEBUG_TYPE
470#define DEBUG_TYPE "foo"
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]471DOUT &lt;&lt; "'foo' debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]472#undef DEBUG_TYPE
473#define DEBUG_TYPE "bar"
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]474DOUT &lt;&lt; "'bar' debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]475#undef DEBUG_TYPE
476#define DEBUG_TYPE ""
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]477DOUT &lt;&lt; "No debug type (2)\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]478</pre>
479</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]480
481<p>Then you can run your pass like this:</p>
482
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]483<div class="doc_code">
484<pre>
485$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]486<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]487$ opt &lt; a.bc &gt; /dev/null -mypass -debug
488No debug type
489'foo' debug type
490'bar' debug type
491No debug type (2)
492$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo
493'foo' debug type
494$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar
495'bar' debug type
496</pre>
497</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]498
499<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
500a 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]501you <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]502<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
503"bar", because there is no system in place to ensure that names do not
504conflict. If two different modules use the same string, they will all be turned
505on when the name is specified. This allows, for example, all debug information
506for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]507even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]508
509</div>
510
511<!-- ======================================================================= -->
512<div class="doc_subsection">
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]513 <a name="Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]514 option</a>
515</div>
516
517<div class="doc_text">
518
519<p>The "<tt><a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]520href="/doxygen/Statistic_8h-source.html">llvm/ADT/Statistic.h</a></tt>" file
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]521provides a class named <tt>Statistic</tt> that is used as a unified way to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]522keep track of what the LLVM compiler is doing and how effective various
523optimizations are. It is useful to see what optimizations are contributing to
524making a particular program run faster.</p>
525
526<p>Often you may run your pass on some big program, and you're interested to see
527how many times it makes a certain transformation. Although you can do this with
528hand inspection, or some ad-hoc method, this is a real pain and not very useful
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]529for big programs. Using the <tt>Statistic</tt> class makes it very easy to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]530keep track of this information, and the calculated information is presented in a
531uniform manner with the rest of the passes being executed.</p>
532
533<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
534it are as follows:</p>
535
536<ol>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]537 <li><p>Define your statistic like this:</p>
538
539<div class="doc_code">
540<pre>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]541#define <a href="#DEBUG_TYPE">DEBUG_TYPE</a> "mypassname" <i>// This goes before any #includes.</i>
542STATISTIC(NumXForms, "The # of times I did stuff");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]543</pre>
544</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]545
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]546 <p>The <tt>STATISTIC</tt> macro defines a static variable, whose name is
547 specified by the first argument. The pass name is taken from the DEBUG_TYPE
548 macro, and the description is taken from the second argument. The variable
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]549 defined ("NumXForms" in this case) acts like an unsigned integer.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]550
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]551 <li><p>Whenever you make a transformation, bump the counter:</p>
552
553<div class="doc_code">
554<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]555++NumXForms; // <i>I did stuff!</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]556</pre>
557</div>
558
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]559 </li>
560 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]561
562 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
563 statistics gathered, use the '<tt>-stats</tt>' option:</p>
564
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]565<div class="doc_code">
566<pre>
567$ opt -stats -mypassname &lt; program.bc &gt; /dev/null
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]568<i>... statistics output ...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]569</pre>
570</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]571
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]572 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
573suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]574
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]575<div class="doc_code">
576<pre>
577 7646 bytecodewriter - Number of normal instructions
578 725 bytecodewriter - Number of oversized instructions
579 129996 bytecodewriter - Number of bytecode bytes written
580 2817 raise - Number of insts DCEd or constprop'd
581 3213 raise - Number of cast-of-self removed
582 5046 raise - Number of expression trees converted
583 75 raise - Number of other getelementptr's formed
584 138 raise - Number of load/store peepholes
585 42 deadtypeelim - Number of unused typenames removed from symtab
586 392 funcresolve - Number of varargs functions resolved
587 27 globaldce - Number of global variables removed
588 2 adce - Number of basic blocks removed
589 134 cee - Number of branches revectored
590 49 cee - Number of setcc instruction eliminated
591 532 gcse - Number of loads removed
592 2919 gcse - Number of instructions removed
593 86 indvars - Number of canonical indvars added
594 87 indvars - Number of aux indvars removed
595 25 instcombine - Number of dead inst eliminate
596 434 instcombine - Number of insts combined
597 248 licm - Number of load insts hoisted
598 1298 licm - Number of insts hoisted to a loop pre-header
599 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
600 75 mem2reg - Number of alloca's promoted
601 1444 cfgsimplify - Number of blocks simplified
602</pre>
603</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]604
605<p>Obviously, with so many optimizations, having a unified framework for this
606stuff is very nice. Making your pass fit well into the framework makes it more
607maintainable and useful.</p>
608
609</div>
610
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]611<!-- ======================================================================= -->
612<div class="doc_subsection">
613 <a name="ViewGraph">Viewing graphs while debugging code</a>
614</div>
615
616<div class="doc_text">
617
618<p>Several of the important data structures in LLVM are graphs: for example
619CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
620LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
621<a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
622DAGs</a>. In many cases, while debugging various parts of the compiler, it is
623nice to instantly visualize these graphs.</p>
624
625<p>LLVM provides several callbacks that are available in a debug build to do
626exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
627the current LLVM tool will pop up a window containing the CFG for the function
628where each basic block is a node in the graph, and each node contains the
629instructions in the block. Similarly, there also exists
630<tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
631<tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
632and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]633you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]634up a window. Alternatively, you can sprinkle calls to these functions in your
635code in places you want to debug.</p>
636
637<p>Getting this to work requires a small amount of configuration. On Unix
638systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
639toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
640Mac OS/X, download and install the Mac OS/X <a
641href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
642<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
643it) to your path. Once in your system and path are set up, rerun the LLVM
644configure script and rebuild LLVM to enable this functionality.</p>
645
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]646<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
647<i>interesting</i> nodes in large complex graphs. From gdb, if you
648<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
649next <tt>call DAG.viewGraph()</tt> would hilight the node in the
650specified color (choices of colors can be found at <a
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]651href="http://www.graphviz.org/doc/info/colors.html">colors</a>.) More
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]652complex node attributes can be provided with <tt>call
653DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
654found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
655Attributes</a>.) If you want to restart and clear all the current graph
656attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
657
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]658</div>
659
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]660<!-- *********************************************************************** -->
661<div class="doc_section">
662 <a name="datastructure">Picking the Right Data Structure for a Task</a>
663</div>
664<!-- *********************************************************************** -->
665
666<div class="doc_text">
667
668<p>LLVM has a plethora of datastructures in the <tt>llvm/ADT/</tt> directory,
669 and we commonly use STL datastructures. This section describes the tradeoffs
670 you should consider when you pick one.</p>
671
672<p>
673The first step is a choose your own adventure: do you want a sequential
674container, a set-like container, or a map-like container? The most important
675thing when choosing a container is the algorithmic properties of how you plan to
676access the container. Based on that, you should use:</p>
677
678<ul>
679<li>a <a href="#ds_map">map-like</a> container if you need efficient lookup
680 of an value based on another value. Map-like containers also support
681 efficient queries for containment (whether a key is in the map). Map-like
682 containers generally do not support efficient reverse mapping (values to
683 keys). If you need that, use two maps. Some map-like containers also
684 support efficient iteration through the keys in sorted order. Map-like
685 containers are the most expensive sort, only use them if you need one of
686 these capabilities.</li>
687
688<li>a <a href="#ds_set">set-like</a> container if you need to put a bunch of
689 stuff into a container that automatically eliminates duplicates. Some
690 set-like containers support efficient iteration through the elements in
691 sorted order. Set-like containers are more expensive than sequential
692 containers.
693</li>
694
695<li>a <a href="#ds_sequential">sequential</a> container provides
696 the most efficient way to add elements and keeps track of the order they are
697 added to the collection. They permit duplicates and support efficient
698 iteration, but do not support efficient lookup based on a key.
699</li>
700
701</ul>
702
703<p>
704Once the proper catagory of container is determined, you can fine tune the
705memory use, constant factors, and cache behaviors of access by intelligently
706picking a member of the catagory. Note that constant factors and cache behavior
707can be a big deal. If you have a vector that usually only contains a few
708elements (but could contain many), for example, it's much better to use
709<a href="#dss_smallvector">SmallVector</a> than <a href="#dss_vector">vector</a>
710. Doing so avoids (relatively) expensive malloc/free calls, which dwarf the
711cost of adding the elements to the container. </p>
712
713</div>
714
715<!-- ======================================================================= -->
716<div class="doc_subsection">
717 <a name="ds_sequential">Sequential Containers (std::vector, std::list, etc)</a>
718</div>
719
720<div class="doc_text">
721There are a variety of sequential containers available for you, based on your
722needs. Pick the first in this section that will do what you want.
723</div>
724
725<!-- _______________________________________________________________________ -->
726<div class="doc_subsubsection">
727 <a name="dss_fixedarrays">Fixed Size Arrays</a>
728</div>
729
730<div class="doc_text">
731<p>Fixed size arrays are very simple and very fast. They are good if you know
732exactly how many elements you have, or you have a (low) upper bound on how many
733you have.</p>
734</div>
735
736<!-- _______________________________________________________________________ -->
737<div class="doc_subsubsection">
738 <a name="dss_heaparrays">Heap Allocated Arrays</a>
739</div>
740
741<div class="doc_text">
742<p>Heap allocated arrays (new[] + delete[]) are also simple. They are good if
743the number of elements is variable, if you know how many elements you will need
744before the array is allocated, and if the array is usually large (if not,
745consider a <a href="#dss_smallvector">SmallVector</a>). The cost of a heap
746allocated array is the cost of the new/delete (aka malloc/free). Also note that
747if you are allocating an array of a type with a constructor, the constructor and
748destructors will be run for every element in the array (resizable vectors only
749construct those elements actually used).</p>
750</div>
751
752<!-- _______________________________________________________________________ -->
753<div class="doc_subsubsection">
754 <a name="dss_smallvector">"llvm/ADT/SmallVector.h"</a>
755</div>
756
757<div class="doc_text">
758<p><tt>SmallVector&lt;Type, N&gt;</tt> is a simple class that looks and smells
759just like <tt>vector&lt;Type&gt;</tt>:
760it supports efficient iteration, lays out elements in memory order (so you can
761do pointer arithmetic between elements), supports efficient push_back/pop_back
762operations, supports efficient random access to its elements, etc.</p>
763
764<p>The advantage of SmallVector is that it allocates space for
765some number of elements (N) <b>in the object itself</b>. Because of this, if
766the SmallVector is dynamically smaller than N, no malloc is performed. This can
767be a big win in cases where the malloc/free call is far more expensive than the
768code that fiddles around with the elements.</p>
769
770<p>This is good for vectors that are "usually small" (e.g. the number of
771predecessors/successors of a block is usually less than 8). On the other hand,
772this makes the size of the SmallVector itself large, so you don't want to
773allocate lots of them (doing so will waste a lot of space). As such,
774SmallVectors are most useful when on the stack.</p>
775
776<p>SmallVector also provides a nice portable and efficient replacement for
777<tt>alloca</tt>.</p>
778
779</div>
780
781<!-- _______________________________________________________________________ -->
782<div class="doc_subsubsection">
783 <a name="dss_vector">&lt;vector&gt;</a>
784</div>
785
786<div class="doc_text">
787<p>
788std::vector is well loved and respected. It is useful when SmallVector isn't:
789when the size of the vector is often large (thus the small optimization will
790rarely be a benefit) or if you will be allocating many instances of the vector
791itself (which would waste space for elements that aren't in the container).
792vector is also useful when interfacing with code that expects vectors :).
793</p>
794</div>
795
796<!-- _______________________________________________________________________ -->
797<div class="doc_subsubsection">
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]798 <a name="dss_deque">&lt;deque&gt;</a>
799</div>
800
801<div class="doc_text">
802<p>std::deque is, in some senses, a generalized version of std::vector. Like
803std::vector, it provides constant time random access and other similar
804properties, but it also provides efficient access to the front of the list. It
805does not guarantee continuity of elements within memory.</p>
806
807<p>In exchange for this extra flexibility, std::deque has significantly higher
808constant factor costs than std::vector. If possible, use std::vector or
809something cheaper.</p>
810</div>
811
812<!-- _______________________________________________________________________ -->
813<div class="doc_subsubsection">
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]814 <a name="dss_list">&lt;list&gt;</a>
815</div>
816
817<div class="doc_text">
818<p>std::list is an extremely inefficient class that is rarely useful.
819It performs a heap allocation for every element inserted into it, thus having an
820extremely high constant factor, particularly for small data types. std::list
821also only supports bidirectional iteration, not random access iteration.</p>
822
823<p>In exchange for this high cost, std::list supports efficient access to both
824ends of the list (like std::deque, but unlike std::vector or SmallVector). In
825addition, the iterator invalidation characteristics of std::list are stronger
826than that of a vector class: inserting or removing an element into the list does
827not invalidate iterator or pointers to other elements in the list.</p>
828</div>
829
830<!-- _______________________________________________________________________ -->
831<div class="doc_subsubsection">
832 <a name="dss_ilist">llvm/ADT/ilist</a>
833</div>
834
835<div class="doc_text">
836<p><tt>ilist&lt;T&gt;</tt> implements an 'intrusive' doubly-linked list. It is
837intrusive, because it requires the element to store and provide access to the
838prev/next pointers for the list.</p>
839
840<p>ilist has the same drawbacks as std::list, and additionally requires an
841ilist_traits implementation for the element type, but it provides some novel
842characteristics. In particular, it can efficiently store polymorphic objects,
843the traits class is informed when an element is inserted or removed from the
844list, and ilists are guaranteed to support a constant-time splice operation.
845</p>
846
847<p>These properties are exactly what we want for things like Instructions and
848basic blocks, which is why these are implemented with ilists.</p>
849</div>
850
851<!-- _______________________________________________________________________ -->
852<div class="doc_subsubsection">
853 <a name="dss_other">Other options</a>
854</div>
855
856<div class="doc_text">
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]857<p>Other STL containers are available, such as std::string.</p>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]858
859<p>There are also various STL adapter classes such as std::queue,
860std::priority_queue, std::stack, etc. These provide simplified access to an
861underlying container but don't affect the cost of the container itself.</p>
862
863</div>
864
865
866<!-- ======================================================================= -->
867<div class="doc_subsection">
868 <a name="ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
869</div>
870
871<div class="doc_text">
872
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]873<p>Set-like containers are useful when you need to canonicalize multiple values
874into a single representation. There are several different choices for how to do
875this, providing various trade-offs.</p>
876
877</div>
878
879
880<!-- _______________________________________________________________________ -->
881<div class="doc_subsubsection">
882 <a name="dss_sortedvectorset">A sorted 'vector'</a>
883</div>
884
885<div class="doc_text">
886
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame^]887<p>If you intend to insert a lot of elements, then do a lot of queries, a
888great approach is to use a vector (or other sequential container) with
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]889std::sort+std::unique to remove duplicates. This approach works really well if
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame^]890your usage pattern has these two distinct phases (insert then query), and can be
891coupled with a good choice of <a href="#ds_sequential">sequential container</a>.
892</p>
893
894<p>
895This combination provides the several nice properties: the result data is
896contiguous in memory (good for cache locality), has few allocations, is easy to
897address (iterators in the final vector are just indices or pointers), and can be
898efficiently queried with a standard binary or radix search.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]899
900</div>
901
902<!-- _______________________________________________________________________ -->
903<div class="doc_subsubsection">
904 <a name="dss_smallset">"llvm/ADT/SmallSet.h"</a>
905</div>
906
907<div class="doc_text">
908
909<p>If you have a set-like datastructure that is usually small and whose elements
Chris Lattner4ddfac12007-02-03 07:59:51 +0000[diff] [blame]910are reasonably small, a <tt>SmallSet&lt;Type, N&gt;</tt> is a good choice. This set
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]911has space for N elements in place (thus, if the set is dynamically smaller than
912N, no malloc traffic is required) and access them with a simple linear search.
913When the set grows beyond 'N', it allocates a more expensive representation that
914guarantees efficient access (for most types, it falls back to std::set, but for
915pointers it uses something far better, see <a
916href="#dss_smallptrset">SmallPtrSet</a>).</p>
917
918<p>The magic of this class is that it handles small sets extremely efficiently,
919but gracefully handles extremely large sets without loss of efficiency. The
920drawback is that the interface is quite small: it supports insertion, queries
921and erasing, but does not support iteration.</p>
922
923</div>
924
925<!-- _______________________________________________________________________ -->
926<div class="doc_subsubsection">
927 <a name="dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a>
928</div>
929
930<div class="doc_text">
931
932<p>SmallPtrSet has all the advantages of SmallSet (and a SmallSet of pointers is
933transparently implemented with a SmallPtrSet), but also suports iterators. If
934more than 'N' allocations are performed, a single quadratically
935probed hash table is allocated and grows as needed, providing extremely
936efficient access (constant time insertion/deleting/queries with low constant
937factors) and is very stingy with malloc traffic.</p>
938
939<p>Note that, unlike std::set, the iterators of SmallPtrSet are invalidated
940whenever an insertion occurs. Also, the values visited by the iterators are not
941visited in sorted order.</p>
942
943</div>
944
945<!-- _______________________________________________________________________ -->
946<div class="doc_subsubsection">
947 <a name="dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a>
948</div>
949
950<div class="doc_text">
951
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]952<p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]953FoldingSet is an aggregate class that is really good at uniquing
954expensive-to-create or polymorphic objects. It is a combination of a chained
955hash table with intrusive links (uniqued objects are required to inherit from
956FoldingSetNode) that uses SmallVector as part of its ID process.</p>
957
958<p>Consider a case where you want to implement a "getorcreate_foo" method for
959a complex object (for example, a node in the code generator). The client has a
960description of *what* it wants to generate (it knows the opcode and all the
961operands), but we don't want to 'new' a node, then try inserting it into a set
962only to find out it already exists (at which point we would have to delete it
963and return the node that already exists).
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]964</p>
965
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]966<p>To support this style of client, FoldingSet perform a query with a
967FoldingSetNodeID (which wraps SmallVector) that can be used to describe the
968element that we want to query for. The query either returns the element
969matching the ID or it returns an opaque ID that indicates where insertion should
970take place.</p>
971
972<p>Because FoldingSet uses intrusive links, it can support polymorphic objects
973in the set (for example, you can have SDNode instances mixed with LoadSDNodes).
974Because the elements are individually allocated, pointers to the elements are
975stable: inserting or removing elements does not invalidate any pointers to other
976elements.
977</p>
978
979</div>
980
981<!-- _______________________________________________________________________ -->
982<div class="doc_subsubsection">
983 <a name="dss_set">&lt;set&gt;</a>
984</div>
985
986<div class="doc_text">
987
988<p>std::set is a reasonable all-around set class, which is good at many things
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame^]989but great at nothing. std::set allocates memory for each element
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]990inserted (thus it is very malloc intensive) and typically stores three pointers
991with every element (thus adding a large amount of per-element space overhead).
992It offers guaranteed log(n) performance, which is not particularly fast.
993</p>
994
995<p>The advantages of std::set is that its iterators are stable (deleting or
996inserting an element from the set does not affect iterators or pointers to other
997elements) and that iteration over the set is guaranteed to be in sorted order.
998If the elements in the set are large, then the relative overhead of the pointers
999and malloc traffic is not a big deal, but if the elements of the set are small,
1000std::set is almost never a good choice.</p>
1001
1002</div>
1003
1004<!-- _______________________________________________________________________ -->
1005<div class="doc_subsubsection">
1006 <a name="dss_setvector">"llvm/ADT/SetVector.h"</a>
1007</div>
1008
1009<div class="doc_text">
1010<p>LLVM's SetVector&lt;Type&gt; is actually a combination of a set along with
1011a <a href="#ds_sequential">Sequential Container</a>. The important property
1012that this provides is efficient insertion with uniquing (duplicate elements are
1013ignored) with iteration support. It implements this by inserting elements into
1014both a set-like container and the sequential container, using the set-like
1015container for uniquing and the sequential container for iteration.
1016</p>
1017
1018<p>The difference between SetVector and other sets is that the order of
1019iteration is guaranteed to match the order of insertion into the SetVector.
1020This property is really important for things like sets of pointers. Because
1021pointer values are non-deterministic (e.g. vary across runs of the program on
1022different machines), iterating over the pointers in a std::set or other set will
1023not be in a well-defined order.</p>
1024
1025<p>
1026The drawback of SetVector is that it requires twice as much space as a normal
1027set and has the sum of constant factors from the set-like container and the
1028sequential container that it uses. Use it *only* if you need to iterate over
1029the elements in a deterministic order. SetVector is also expensive to delete
1030elements out of (linear time).
1031</p>
1032
1033</div>
1034
1035<!-- _______________________________________________________________________ -->
1036<div class="doc_subsubsection">
1037 <a name="dss_otherset">Other Options</a>
1038</div>
1039
1040<div class="doc_text">
1041
1042<p>
1043The STL provides several other options, such as std::multiset and the various
1044"hash_set" like containers (whether from C++TR1 or from the SGI library).</p>
1045
1046<p>std::multiset is useful if you're not interested in elimination of
1047duplicates, but has all the drawbacks of std::set. A sorted vector or some
1048other approach is almost always better.</p>
1049
1050<p>The various hash_set implementations (exposed portably by
1051"llvm/ADT/hash_set") is a standard chained hashtable. This algorithm is malloc
1052intensive like std::set (performing an allocation for each element inserted,
1053thus having really high constant factors) but (usually) provides O(1)
1054insertion/deletion of elements. This can be useful if your elements are large
1055(thus making the constant-factor cost relatively low). Element iteration does
1056not visit elements in a useful order.</p>
1057
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1058</div>
1059
1060<!-- ======================================================================= -->
1061<div class="doc_subsection">
1062 <a name="ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
1063</div>
1064
1065<div class="doc_text">
1066sorted vector
1067std::map
1068DenseMap
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1069UniqueVector
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1070IndexedMap
1071hash_map
1072CStringMap
1073</div>
1074
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]1075
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1076<!-- *********************************************************************** -->
1077<div class="doc_section">
1078 <a name="common">Helpful Hints for Common Operations</a>
1079</div>
1080<!-- *********************************************************************** -->
1081
1082<div class="doc_text">
1083
1084<p>This section describes how to perform some very simple transformations of
1085LLVM code. This is meant to give examples of common idioms used, showing the
1086practical side of LLVM transformations. <p> Because this is a "how-to" section,
1087you should also read about the main classes that you will be working with. The
1088<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
1089and descriptions of the main classes that you should know about.</p>
1090
1091</div>
1092
1093<!-- NOTE: this section should be heavy on example code -->
1094<!-- ======================================================================= -->
1095<div class="doc_subsection">
1096 <a name="inspection">Basic Inspection and Traversal Routines</a>
1097</div>
1098
1099<div class="doc_text">
1100
1101<p>The LLVM compiler infrastructure have many different data structures that may
1102be traversed. Following the example of the C++ standard template library, the
1103techniques used to traverse these various data structures are all basically the
1104same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
1105method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
1106function returns an iterator pointing to one past the last valid element of the
1107sequence, and there is some <tt>XXXiterator</tt> data type that is common
1108between the two operations.</p>
1109
1110<p>Because the pattern for iteration is common across many different aspects of
1111the program representation, the standard template library algorithms may be used
1112on them, and it is easier to remember how to iterate. First we show a few common
1113examples of the data structures that need to be traversed. Other data
1114structures are traversed in very similar ways.</p>
1115
1116</div>
1117
1118<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1119<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1120 <a name="iterate_function">Iterating over the </a><a
1121 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
1122 href="#Function"><tt>Function</tt></a>
1123</div>
1124
1125<div class="doc_text">
1126
1127<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
1128transform in some way; in particular, you'd like to manipulate its
1129<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
1130the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
1131an example that prints the name of a <tt>BasicBlock</tt> and the number of
1132<tt>Instruction</tt>s it contains:</p>
1133
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1134<div class="doc_code">
1135<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1136// <i>func is a pointer to a Function instance</i>
1137for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i)
1138 // <i>Print out the name of the basic block if it has one, and then the</i>
1139 // <i>number of instructions that it contains</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1140 llvm::cerr &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has "
1141 &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1142</pre>
1143</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1144
1145<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]1146invoking member functions of the <tt>Instruction</tt> class. This is
1147because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]1148classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1149exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
1150
1151</div>
1152
1153<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1154<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1155 <a name="iterate_basicblock">Iterating over the </a><a
1156 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1157 href="#BasicBlock"><tt>BasicBlock</tt></a>
1158</div>
1159
1160<div class="doc_text">
1161
1162<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
1163easy to iterate over the individual instructions that make up
1164<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
1165a <tt>BasicBlock</tt>:</p>
1166
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1167<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1168<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1169// <i>blk is a pointer to a BasicBlock instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1170for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1171 // <i>The next statement works since operator&lt;&lt;(ostream&amp;,...)</i>
1172 // <i>is overloaded for Instruction&amp;</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1173 llvm::cerr &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1174</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1175</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1176
1177<p>However, this isn't really the best way to print out the contents of a
1178<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
1179anything you'll care about, you could have just invoked the print routine on the
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1180basic block itself: <tt>llvm::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1181
1182</div>
1183
1184<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1185<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1186 <a name="iterate_institer">Iterating over the </a><a
1187 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1188 href="#Function"><tt>Function</tt></a>
1189</div>
1190
1191<div class="doc_text">
1192
1193<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
1194<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
1195<tt>InstIterator</tt> should be used instead. You'll need to include <a
1196href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
1197and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1198small 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]1199
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1200<div class="doc_code">
1201<pre>
1202#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
1203
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1204// <i>F is a ptr to a Function instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1205for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1206 llvm::cerr &lt;&lt; *i &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1207</pre>
1208</div>
1209
1210<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]1211worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1212initialize a worklist to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1213F, all you would need to do is something like:</p>
1214
1215<div class="doc_code">
1216<pre>
1217std::set&lt;Instruction*&gt; worklist;
1218worklist.insert(inst_begin(F), inst_end(F));
1219</pre>
1220</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1221
1222<p>The STL set <tt>worklist</tt> would now contain all instructions in the
1223<tt>Function</tt> pointed to by F.</p>
1224
1225</div>
1226
1227<!-- _______________________________________________________________________ -->
1228<div class="doc_subsubsection">
1229 <a name="iterate_convert">Turning an iterator into a class pointer (and
1230 vice-versa)</a>
1231</div>
1232
1233<div class="doc_text">
1234
1235<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]1236instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1237a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1238Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1239is a <tt>BasicBlock::const_iterator</tt>:</p>
1240
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1241<div class="doc_code">
1242<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1243Instruction&amp; inst = *i; // <i>Grab reference to instruction reference</i>
1244Instruction* pinst = &amp;*i; // <i>Grab pointer to instruction reference</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1245const Instruction&amp; inst = *j;
1246</pre>
1247</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1248
1249<p>However, the iterators you'll be working with in the LLVM framework are
1250special: they will automatically convert to a ptr-to-instance type whenever they
1251need to. Instead of dereferencing the iterator and then taking the address of
1252the result, you can simply assign the iterator to the proper pointer type and
1253you get the dereference and address-of operation as a result of the assignment
1254(behind the scenes, this is a result of overloading casting mechanisms). Thus
1255the last line of the last example,</p>
1256
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1257<div class="doc_code">
1258<pre>
1259Instruction* pinst = &amp;*i;
1260</pre>
1261</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1262
1263<p>is semantically equivalent to</p>
1264
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1265<div class="doc_code">
1266<pre>
1267Instruction* pinst = i;
1268</pre>
1269</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1270
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1271<p>It's also possible to turn a class pointer into the corresponding iterator,
1272and this is a constant time operation (very efficient). The following code
1273snippet illustrates use of the conversion constructors provided by LLVM
1274iterators. By using these, you can explicitly grab the iterator of something
1275without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1276
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1277<div class="doc_code">
1278<pre>
1279void printNextInstruction(Instruction* inst) {
1280 BasicBlock::iterator it(inst);
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1281 ++it; // <i>After this line, it refers to the instruction after *inst</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1282 if (it != inst-&gt;getParent()-&gt;end()) llvm::cerr &lt;&lt; *it &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1283}
1284</pre>
1285</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1286
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1287</div>
1288
1289<!--_______________________________________________________________________-->
1290<div class="doc_subsubsection">
1291 <a name="iterate_complex">Finding call sites: a slightly more complex
1292 example</a>
1293</div>
1294
1295<div class="doc_text">
1296
1297<p>Say that you're writing a FunctionPass and would like to count all the
1298locations in the entire module (that is, across every <tt>Function</tt>) where a
1299certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
1300learn 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]1301much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1302you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
1303is what we want to do:</p>
1304
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1305<div class="doc_code">
1306<pre>
1307initialize callCounter to zero
1308for each Function f in the Module
1309 for each BasicBlock b in f
1310 for each Instruction i in b
1311 if (i is a CallInst and calls the given function)
1312 increment callCounter
1313</pre>
1314</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1315
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1316<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1317<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1318override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1319
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1320<div class="doc_code">
1321<pre>
1322Function* targetFunc = ...;
1323
1324class OurFunctionPass : public FunctionPass {
1325 public:
1326 OurFunctionPass(): callCounter(0) { }
1327
1328 virtual runOnFunction(Function&amp; F) {
1329 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
1330 for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
1331 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
1332 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1333 // <i>We know we've encountered a call instruction, so we</i>
1334 // <i>need to determine if it's a call to the</i>
1335 // <i>function pointed to by m_func or not</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1336
1337 if (callInst-&gt;getCalledFunction() == targetFunc)
1338 ++callCounter;
1339 }
1340 }
1341 }
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1342 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1343
1344 private:
1345 unsigned callCounter;
1346};
1347</pre>
1348</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1349
1350</div>
1351
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]1352<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1353<div class="doc_subsubsection">
1354 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
1355</div>
1356
1357<div class="doc_text">
1358
1359<p>You may have noticed that the previous example was a bit oversimplified in
1360that it did not deal with call sites generated by 'invoke' instructions. In
1361this, and in other situations, you may find that you want to treat
1362<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
1363most-specific common base class is <tt>Instruction</tt>, which includes lots of
1364less closely-related things. For these cases, LLVM provides a handy wrapper
1365class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]1366href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1367It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
1368methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1369<tt>InvokeInst</tt>s.</p>
1370
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1371<p>This class has "value semantics": it should be passed by value, not by
1372reference and it should not be dynamically allocated or deallocated using
1373<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
1374assignable and constructable, with costs equivalents to that of a bare pointer.
1375If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1376
1377</div>
1378
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]1379<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1380<div class="doc_subsubsection">
1381 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
1382</div>
1383
1384<div class="doc_text">
1385
1386<p>Frequently, we might have an instance of the <a
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]1387href="/doxygen/classllvm_1_1Value.html">Value Class</a> and we want to
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1388determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
1389<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
1390For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
1391particular function <tt>foo</tt>. Finding all of the instructions that
1392<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
1393of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1394
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1395<div class="doc_code">
1396<pre>
1397Function* F = ...;
1398
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1399for (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]1400 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1401 llvm::cerr &lt;&lt; "F is used in instruction:\n";
1402 llvm::cerr &lt;&lt; *Inst &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1403 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1404</pre>
1405</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1406
1407<p>Alternately, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1408href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1409<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
1410<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
1411<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
1412all of the values that a particular instruction uses (that is, the operands of
1413the particular <tt>Instruction</tt>):</p>
1414
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1415<div class="doc_code">
1416<pre>
1417Instruction* pi = ...;
1418
1419for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {
1420 Value* v = *i;
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1421 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1422}
1423</pre>
1424</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1425
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]1426<!--
1427 def-use chains ("finding all users of"): Value::use_begin/use_end
1428 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1429-->
1430
1431</div>
1432
1433<!-- ======================================================================= -->
1434<div class="doc_subsection">
1435 <a name="simplechanges">Making simple changes</a>
1436</div>
1437
1438<div class="doc_text">
1439
1440<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]1441infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1442transformations, it's fairly common to manipulate the contents of basic
1443blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1444and gives example code.</p>
1445
1446</div>
1447
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1448<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1449<div class="doc_subsubsection">
1450 <a name="schanges_creating">Creating and inserting new
1451 <tt>Instruction</tt>s</a>
1452</div>
1453
1454<div class="doc_text">
1455
1456<p><i>Instantiating Instructions</i></p>
1457
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1458<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1459constructor for the kind of instruction to instantiate and provide the necessary
1460parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
1461(const-ptr-to) <tt>Type</tt>. Thus:</p>
1462
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1463<div class="doc_code">
1464<pre>
1465AllocaInst* ai = new AllocaInst(Type::IntTy);
1466</pre>
1467</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1468
1469<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
1470one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
1471subclass is likely to have varying default parameters which change the semantics
1472of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1473href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1474Instruction</a> that you're interested in instantiating.</p>
1475
1476<p><i>Naming values</i></p>
1477
1478<p>It is very useful to name the values of instructions when you're able to, as
1479this facilitates the debugging of your transformations. If you end up looking
1480at generated LLVM machine code, you definitely want to have logical names
1481associated with the results of instructions! By supplying a value for the
1482<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
1483associate a logical name with the result of the instruction's execution at
1484runtime. For example, say that I'm writing a transformation that dynamically
1485allocates space for an integer on the stack, and that integer is going to be
1486used as some kind of index by some other code. To accomplish this, I place an
1487<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
1488<tt>Function</tt>, and I'm intending to use it within the same
1489<tt>Function</tt>. I might do:</p>
1490
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1491<div class="doc_code">
1492<pre>
1493AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");
1494</pre>
1495</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1496
1497<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
1498execution value, which is a pointer to an integer on the runtime stack.</p>
1499
1500<p><i>Inserting instructions</i></p>
1501
1502<p>There are essentially two ways to insert an <tt>Instruction</tt>
1503into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
1504
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]1505<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1506 <li>Insertion into an explicit instruction list
1507
1508 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
1509 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
1510 before <tt>*pi</tt>, we do the following: </p>
1511
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1512<div class="doc_code">
1513<pre>
1514BasicBlock *pb = ...;
1515Instruction *pi = ...;
1516Instruction *newInst = new Instruction(...);
1517
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1518pb-&gt;getInstList().insert(pi, newInst); // <i>Inserts newInst before pi in pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1519</pre>
1520</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1521
1522 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
1523 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
1524 classes provide constructors which take a pointer to a
1525 <tt>BasicBlock</tt> to be appended to. For example code that
1526 looked like: </p>
1527
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1528<div class="doc_code">
1529<pre>
1530BasicBlock *pb = ...;
1531Instruction *newInst = new Instruction(...);
1532
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1533pb-&gt;getInstList().push_back(newInst); // <i>Appends newInst to pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1534</pre>
1535</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1536
1537 <p>becomes: </p>
1538
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1539<div class="doc_code">
1540<pre>
1541BasicBlock *pb = ...;
1542Instruction *newInst = new Instruction(..., pb);
1543</pre>
1544</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1545
1546 <p>which is much cleaner, especially if you are creating
1547 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1548
1549 <li>Insertion into an implicit instruction list
1550
1551 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
1552 are implicitly associated with an existing instruction list: the instruction
1553 list of the enclosing basic block. Thus, we could have accomplished the same
1554 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
1555 </p>
1556
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1557<div class="doc_code">
1558<pre>
1559Instruction *pi = ...;
1560Instruction *newInst = new Instruction(...);
1561
1562pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);
1563</pre>
1564</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1565
1566 <p>In fact, this sequence of steps occurs so frequently that the
1567 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
1568 constructors which take (as a default parameter) a pointer to an
1569 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
1570 precede. That is, <tt>Instruction</tt> constructors are capable of
1571 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
1572 provided instruction, immediately before that instruction. Using an
1573 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
1574 parameter, the above code becomes:</p>
1575
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1576<div class="doc_code">
1577<pre>
1578Instruction* pi = ...;
1579Instruction* newInst = new Instruction(..., pi);
1580</pre>
1581</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1582
1583 <p>which is much cleaner, especially if you're creating a lot of
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1584 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1585</ul>
1586
1587</div>
1588
1589<!--_______________________________________________________________________-->
1590<div class="doc_subsubsection">
1591 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
1592</div>
1593
1594<div class="doc_text">
1595
1596<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1597<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1598you must have a pointer to the instruction that you wish to delete. Second, you
1599need to obtain the pointer to that instruction's basic block. You use the
1600pointer to the basic block to get its list of instructions and then use the
1601erase function to remove your instruction. For example:</p>
1602
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1603<div class="doc_code">
1604<pre>
1605<a href="#Instruction">Instruction</a> *I = .. ;
1606<a href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();
1607
1608BB-&gt;getInstList().erase(I);
1609</pre>
1610</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1611
1612</div>
1613
1614<!--_______________________________________________________________________-->
1615<div class="doc_subsubsection">
1616 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
1617 <tt>Value</tt></a>
1618</div>
1619
1620<div class="doc_text">
1621
1622<p><i>Replacing individual instructions</i></p>
1623
1624<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]1625permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1626and <tt>ReplaceInstWithInst</tt>.</p>
1627
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1628<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1629
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1630<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1631 <li><tt>ReplaceInstWithValue</tt>
1632
1633 <p>This function replaces all uses (within a basic block) of a given
1634 instruction with a value, and then removes the original instruction. The
1635 following example illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1636 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1637 pointer to an integer.</p>
1638
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1639<div class="doc_code">
1640<pre>
1641AllocaInst* instToReplace = ...;
1642BasicBlock::iterator ii(instToReplace);
1643
1644ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1645 Constant::getNullValue(PointerType::get(Type::IntTy)));
1646</pre></div></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1647
1648 <li><tt>ReplaceInstWithInst</tt>
1649
1650 <p>This function replaces a particular instruction with another
1651 instruction. The following example illustrates the replacement of one
1652 <tt>AllocaInst</tt> with another.</p>
1653
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1654<div class="doc_code">
1655<pre>
1656AllocaInst* instToReplace = ...;
1657BasicBlock::iterator ii(instToReplace);
1658
1659ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1660 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));
1661</pre></div></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1662</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1663
1664<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
1665
1666<p>You can use <tt>Value::replaceAllUsesWith</tt> and
1667<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]1668doxygen documentation for the <a href="/doxygen/classllvm_1_1Value.html">Value Class</a>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1669and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1670information.</p>
1671
1672<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
1673include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
1674ReplaceInstWithValue, ReplaceInstWithInst -->
1675
1676</div>
1677
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1678<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1679<div class="doc_section">
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1680 <a name="advanced">Advanced Topics</a>
1681</div>
1682<!-- *********************************************************************** -->
1683
1684<div class="doc_text">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1685<p>
1686This section describes some of the advanced or obscure API's that most clients
1687do not need to be aware of. These API's tend manage the inner workings of the
1688LLVM system, and only need to be accessed in unusual circumstances.
1689</p>
1690</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1691
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1692<!-- ======================================================================= -->
1693<div class="doc_subsection">
1694 <a name="TypeResolve">LLVM Type Resolution</a>
1695</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1696
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1697<div class="doc_text">
1698
1699<p>
1700The LLVM type system has a very simple goal: allow clients to compare types for
1701structural equality with a simple pointer comparison (aka a shallow compare).
1702This goal makes clients much simpler and faster, and is used throughout the LLVM
1703system.
1704</p>
1705
1706<p>
1707Unfortunately achieving this goal is not a simple matter. In particular,
1708recursive types and late resolution of opaque types makes the situation very
1709difficult to handle. Fortunately, for the most part, our implementation makes
1710most clients able to be completely unaware of the nasty internal details. The
1711primary case where clients are exposed to the inner workings of it are when
1712building a recursive type. In addition to this case, the LLVM bytecode reader,
1713assembly parser, and linker also have to be aware of the inner workings of this
1714system.
1715</p>
1716
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1717<p>
1718For our purposes below, we need three concepts. First, an "Opaque Type" is
1719exactly as defined in the <a href="LangRef.html#t_opaque">language
1720reference</a>. Second an "Abstract Type" is any type which includes an
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1721opaque type as part of its type graph (for example "<tt>{ opaque, i32 }</tt>").
1722Third, a concrete type is a type that is not an abstract type (e.g. "<tt>{ i32,
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1723float }</tt>").
1724</p>
1725
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1726</div>
1727
1728<!-- ______________________________________________________________________ -->
1729<div class="doc_subsubsection">
1730 <a name="BuildRecType">Basic Recursive Type Construction</a>
1731</div>
1732
1733<div class="doc_text">
1734
1735<p>
1736Because the most common question is "how do I build a recursive type with LLVM",
1737we answer it now and explain it as we go. Here we include enough to cause this
1738to be emitted to an output .ll file:
1739</p>
1740
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1741<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1742<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1743%mylist = type { %mylist*, i32 }
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1744</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1745</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1746
1747<p>
1748To build this, use the following LLVM APIs:
1749</p>
1750
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1751<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1752<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1753// <i>Create the initial outer struct</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1754<a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
1755std::vector&lt;const Type*&gt; Elts;
1756Elts.push_back(PointerType::get(StructTy));
1757Elts.push_back(Type::IntTy);
1758StructType *NewSTy = StructType::get(Elts);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1759
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1760// <i>At this point, NewSTy = "{ opaque*, i32 }". Tell VMCore that</i>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1761// <i>the struct and the opaque type are actually the same.</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1762cast&lt;OpaqueType&gt;(StructTy.get())-&gt;<a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1763
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1764// <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]1765// <i>kept up-to-date</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1766NewSTy = cast&lt;StructType&gt;(StructTy.get());
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1767
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1768// <i>Add a name for the type to the module symbol table (optional)</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1769MyModule-&gt;addTypeName("mylist", NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1770</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1771</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1772
1773<p>
1774This code shows the basic approach used to build recursive types: build a
1775non-recursive type using 'opaque', then use type unification to close the cycle.
1776The type unification step is performed by the <tt><a
Chris Lattneraff26d12007-02-03 03:06:52 +0000[diff] [blame]1777href="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1778described next. After that, we describe the <a
1779href="#PATypeHolder">PATypeHolder class</a>.
1780</p>
1781
1782</div>
1783
1784<!-- ______________________________________________________________________ -->
1785<div class="doc_subsubsection">
1786 <a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
1787</div>
1788
1789<div class="doc_text">
1790<p>
1791The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
1792While this method is actually a member of the DerivedType class, it is most
1793often used on OpaqueType instances. Type unification is actually a recursive
1794process. After unification, types can become structurally isomorphic to
1795existing types, and all duplicates are deleted (to preserve pointer equality).
1796</p>
1797
1798<p>
1799In the example above, the OpaqueType object is definitely deleted.
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1800Additionally, if there is an "{ \2*, i32}" type already created in the system,
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1801the pointer and struct type created are <b>also</b> deleted. Obviously whenever
1802a type is deleted, any "Type*" pointers in the program are invalidated. As
1803such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
1804live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
1805types can never move or be deleted). To deal with this, the <a
1806href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
1807reference to a possibly refined type, and the <a
1808href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
1809complex datastructures.
1810</p>
1811
1812</div>
1813
1814<!-- ______________________________________________________________________ -->
1815<div class="doc_subsubsection">
1816 <a name="PATypeHolder">The PATypeHolder Class</a>
1817</div>
1818
1819<div class="doc_text">
1820<p>
1821PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
1822happily goes about nuking types that become isomorphic to existing types, it
1823automatically updates all PATypeHolder objects to point to the new type. In the
1824example above, this allows the code to maintain a pointer to the resultant
1825resolved recursive type, even though the Type*'s are potentially invalidated.
1826</p>
1827
1828<p>
1829PATypeHolder is an extremely light-weight object that uses a lazy union-find
1830implementation to update pointers. For example the pointer from a Value to its
1831Type is maintained by PATypeHolder objects.
1832</p>
1833
1834</div>
1835
1836<!-- ______________________________________________________________________ -->
1837<div class="doc_subsubsection">
1838 <a name="AbstractTypeUser">The AbstractTypeUser Class</a>
1839</div>
1840
1841<div class="doc_text">
1842
1843<p>
1844Some data structures need more to perform more complex updates when types get
1845resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
1846move and potentially merge type planes in its representation when a pointer
1847changes.</p>
1848
1849<p>
1850To support this, a class can derive from the AbstractTypeUser class. This class
1851allows it to get callbacks when certain types are resolved. To register to get
1852callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1853methods can be called on a type. Note that these methods only work for <i>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1854 abstract</i> types. Concrete types (those that do not include any opaque
1855objects) can never be refined.
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1856</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1857</div>
1858
1859
1860<!-- ======================================================================= -->
1861<div class="doc_subsection">
1862 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
1863</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1864
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1865<div class="doc_text">
1866<p>This class provides a symbol table that the <a
1867href="#Function"><tt>Function</tt></a> and <a href="#Module">
1868<tt>Module</tt></a> classes use for naming definitions. The symbol table can
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1869provide a name for any <a href="#Value"><tt>Value</tt></a>.
1870<tt>SymbolTable</tt> is an abstract data type. It hides the data it contains
1871and provides access to it through a controlled interface.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1872
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1873<p>Note that the <tt>SymbolTable</tt> class should not be directly accessed
1874by most clients. It should only be used when iteration over the symbol table
1875names themselves are required, which is very special purpose. Note that not
1876all LLVM
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1877<a href="#Value">Value</a>s have names, and those without names (i.e. they have
1878an empty name) do not exist in the symbol table.
1879</p>
1880
1881<p>To use the <tt>SymbolTable</tt> well, you need to understand the
1882structure of the information it holds. The class contains two
1883<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
1884<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1885Thus, Values are stored in two-dimensions and accessed by <tt>Type</tt> and
1886name.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1887
1888<p>The interface of this class provides three basic types of operations:
1889<ol>
1890 <li><em>Accessors</em>. Accessors provide read-only access to information
1891 such as finding a value for a name with the
1892 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1893 <li><em>Mutators</em>. Mutators allow the user to add information to the
1894 <tt>SymbolTable</tt> with methods like
1895 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1896 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1897 of the symbol table in well defined ways, such as the method
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1898 <a href="#SymbolTable_plane_begin"><tt>plane_begin</tt></a>.</li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1899</ol>
1900
1901<h3>Accessors</h3>
1902<dl>
1903 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
1904 </dt>
1905 <dd>The <tt>lookup</tt> method searches the type plane given by the
1906 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1907 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1908
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1909 <dt><tt>bool isEmpty() const</tt>:</dt>
1910 <dd>This function returns true if both the value and types maps are
1911 empty</dd>
1912</dl>
1913
1914<h3>Mutators</h3>
1915<dl>
1916 <dt><tt>void insert(Value *Val)</tt>:</dt>
1917 <dd>This method adds the provided value to the symbol table. The Value must
1918 have both a name and a type which are extracted and used to place the value
1919 in the correct type plane under the value's name.</dd>
1920
1921 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1922 <dd> Inserts a constant or type into the symbol table with the specified
1923 name. There can be a many to one mapping between names and constants
1924 or types.</dd>
1925
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1926 <dt><tt>void remove(Value* Val)</tt>:</dt>
1927 <dd> This method removes a named value from the symbol table. The
1928 type and name of the Value are extracted from \p N and used to
1929 lookup the Value in the correct type plane. If the Value is
1930 not in the symbol table, this method silently ignores the
1931 request.</dd>
1932
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1933 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1934 <dd> Remove a constant or type with the specified name from the
1935 symbol table.</dd>
1936
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1937 <dt><tt>Value *remove(const value_iterator&amp; It)</tt>:</dt>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1938 <dd> Removes a specific value from the symbol table.
1939 Returns the removed value.</dd>
1940
1941 <dt><tt>bool strip()</tt>:</dt>
1942 <dd> This method will strip the symbol table of its names leaving
1943 the type and values. </dd>
1944
1945 <dt><tt>void clear()</tt>:</dt>
1946 <dd>Empty the symbol table completely.</dd>
1947</dl>
1948
1949<h3>Iteration</h3>
1950<p>The following functions describe three types of iterators you can obtain
1951the beginning or end of the sequence for both const and non-const. It is
1952important to keep track of the different kinds of iterators. There are
1953three idioms worth pointing out:</p>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1954
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1955<table>
1956 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1957 <tr>
1958 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1959 <td align="left"><pre><tt>
1960for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1961 PE = ST.plane_end(); PI != PE; ++PI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1962 PI-&gt;first // <i>This is the Type* of the plane</i>
1963 PI-&gt;second // <i>This is the SymbolTable::ValueMap of name/Value pairs</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1964}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1965 </tt></pre></td>
1966 </tr>
1967 <tr>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1968 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1969 <td align="left"><pre><tt>
1970for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1971 VE = ST.value_end(SomeType); VI != VE; ++VI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1972 VI-&gt;first // <i>This is the name of the Value</i>
1973 VI-&gt;second // <i>This is the Value* value associated with the name</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1974}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1975 </tt></pre></td>
1976 </tr>
1977</table>
1978
1979<p>Using the recommended iterator names and idioms will help you avoid
1980making mistakes. Of particular note, make sure that whenever you use
1981value_begin(SomeType) that you always compare the resulting iterator
1982with value_end(SomeType) not value_end(SomeOtherType) or else you
1983will loop infinitely.</p>
1984
1985<dl>
1986
1987 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1988 <dd>Get an iterator that starts at the beginning of the type planes.
1989 The iterator will iterate over the Type/ValueMap pairs in the
1990 type planes. </dd>
1991
1992 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1993 <dd>Get a const_iterator that starts at the beginning of the type
1994 planes. The iterator will iterate over the Type/ValueMap pairs
1995 in the type planes. </dd>
1996
1997 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1998 <dd>Get an iterator at the end of the type planes. This serves as
1999 the marker for end of iteration over the type planes.</dd>
2000
2001 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
2002 <dd>Get a const_iterator at the end of the type planes. This serves as
2003 the marker for end of iteration over the type planes.</dd>
2004
2005 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
2006 <dd>Get an iterator that starts at the beginning of a type plane.
2007 The iterator will iterate over the name/value pairs in the type plane.
2008 Note: The type plane must already exist before using this.</dd>
2009
2010 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
2011 <dd>Get a const_iterator that starts at the beginning of a type plane.
2012 The iterator will iterate over the name/value pairs in the type plane.
2013 Note: The type plane must already exist before using this.</dd>
2014
2015 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
2016 <dd>Get an iterator to the end of a type plane. This serves as the marker
2017 for end of iteration of the type plane.
2018 Note: The type plane must already exist before using this.</dd>
2019
2020 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
2021 <dd>Get a const_iterator to the end of a type plane. This serves as the
2022 marker for end of iteration of the type plane.
2023 Note: the type plane must already exist before using this.</dd>
2024
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2025 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
2026 <dd>This method returns a plane_const_iterator for iteration over
2027 the type planes starting at a specific plane, given by \p Ty.</dd>
2028
2029 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
2030 <dd>This method returns a plane_iterator for iteration over the
2031 type planes starting at a specific plane, given by \p Ty.</dd>
2032
2033</dl>
2034</div>
2035
2036
2037
2038<!-- *********************************************************************** -->
2039<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2040 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
2041</div>
2042<!-- *********************************************************************** -->
2043
2044<div class="doc_text">
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2045<p><tt>#include "<a href="/doxygen/Type_8h-source.html">llvm/Type.h</a>"</tt>
2046<br>doxygen info: <a href="/doxygen/classllvm_1_1Type.html">Type Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2047
2048<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2049being inspected or transformed. The core LLVM classes are defined in
2050header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2051the <tt>lib/VMCore</tt> directory.</p>
2052
2053</div>
2054
2055<!-- ======================================================================= -->
2056<div class="doc_subsection">
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2057 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
2058</div>
2059
2060<div class="doc_text">
2061
2062 <p><tt>Type</tt> is a superclass of all type classes. Every <tt>Value</tt> has
2063 a <tt>Type</tt>. <tt>Type</tt> cannot be instantiated directly but only
2064 through its subclasses. Certain primitive types (<tt>VoidType</tt>,
2065 <tt>LabelType</tt>, <tt>FloatType</tt> and <tt>DoubleType</tt>) have hidden
2066 subclasses. They are hidden because they offer no useful functionality beyond
2067 what the <tt>Type</tt> class offers except to distinguish themselves from
2068 other subclasses of <tt>Type</tt>.</p>
2069 <p>All other types are subclasses of <tt>DerivedType</tt>. Types can be
2070 named, but this is not a requirement. There exists exactly
2071 one instance of a given shape at any one time. This allows type equality to
2072 be performed with address equality of the Type Instance. That is, given two
2073 <tt>Type*</tt> values, the types are identical if the pointers are identical.
2074 </p>
2075</div>
2076
2077<!-- _______________________________________________________________________ -->
2078<div class="doc_subsubsection">
2079 <a name="m_Value">Important Public Methods</a>
2080</div>
2081
2082<div class="doc_text">
2083
2084<ul>
Chris Lattner8f79df32007-01-15 01:55:32 +0000[diff] [blame]2085 <li><tt>bool isInteger() const</tt>: Returns true for any integer type.</li>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2086
2087 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
2088 floating point types.</li>
2089
2090 <li><tt>bool isAbstract()</tt>: Return true if the type is abstract (contains
2091 an OpaqueType anywhere in its definition).</li>
2092
2093 <li><tt>bool isSized()</tt>: Return true if the type has known size. Things
2094 that don't have a size are abstract types, labels and void.</li>
2095
2096</ul>
2097</div>
2098
2099<!-- _______________________________________________________________________ -->
2100<div class="doc_subsubsection">
2101 <a name="m_Value">Important Derived Types</a>
2102</div>
2103<div class="doc_text">
2104<dl>
2105 <dt><tt>IntegerType</tt></dt>
2106 <dd>Subclass of DerivedType that represents integer types of any bit width.
2107 Any bit width between <tt>IntegerType::MIN_INT_BITS</tt> (1) and
2108 <tt>IntegerType::MAX_INT_BITS</tt> (~8 million) can be represented.
2109 <ul>
2110 <li><tt>static const IntegerType* get(unsigned NumBits)</tt>: get an integer
2111 type of a specific bit width.</li>
2112 <li><tt>unsigned getBitWidth() const</tt>: Get the bit width of an integer
2113 type.</li>
2114 </ul>
2115 </dd>
2116 <dt><tt>SequentialType</tt></dt>
2117 <dd>This is subclassed by ArrayType and PointerType
2118 <ul>
2119 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2120 of the elements in the sequential type. </li>
2121 </ul>
2122 </dd>
2123 <dt><tt>ArrayType</tt></dt>
2124 <dd>This is a subclass of SequentialType and defines the interface for array
2125 types.
2126 <ul>
2127 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2128 elements in the array. </li>
2129 </ul>
2130 </dd>
2131 <dt><tt>PointerType</tt></dt>
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]2132 <dd>Subclass of SequentialType for pointer types.</dd>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2133 <dt><tt>PackedType</tt></dt>
2134 <dd>Subclass of SequentialType for packed (vector) types. A
2135 packed type is similar to an ArrayType but is distinguished because it is
2136 a first class type wherease ArrayType is not. Packed types are used for
2137 vector operations and are usually small vectors of of an integer or floating
2138 point type.</dd>
2139 <dt><tt>StructType</tt></dt>
2140 <dd>Subclass of DerivedTypes for struct types.</dd>
2141 <dt><tt>FunctionType</tt></dt>
2142 <dd>Subclass of DerivedTypes for function types.
2143 <ul>
2144 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2145 function</li>
2146 <li><tt> const Type * getReturnType() const</tt>: Returns the
2147 return type of the function.</li>
2148 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2149 the type of the ith parameter.</li>
2150 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2151 number of formal parameters.</li>
2152 </ul>
2153 </dd>
2154 <dt><tt>OpaqueType</tt></dt>
2155 <dd>Sublcass of DerivedType for abstract types. This class
2156 defines no content and is used as a placeholder for some other type. Note
2157 that OpaqueType is used (temporarily) during type resolution for forward
2158 references of types. Once the referenced type is resolved, the OpaqueType
2159 is replaced with the actual type. OpaqueType can also be used for data
2160 abstraction. At link time opaque types can be resolved to actual types
2161 of the same name.</dd>
2162</dl>
2163</div>
2164
2165<!-- ======================================================================= -->
2166<div class="doc_subsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2167 <a name="Value">The <tt>Value</tt> class</a>
2168</div>
2169
2170<div>
2171
2172<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
2173<br>
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]2174doxygen info: <a href="/doxygen/classllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2175
2176<p>The <tt>Value</tt> class is the most important class in the LLVM Source
2177base. It represents a typed value that may be used (among other things) as an
2178operand to an instruction. There are many different types of <tt>Value</tt>s,
2179such as <a href="#Constant"><tt>Constant</tt></a>s,<a
2180href="#Argument"><tt>Argument</tt></a>s. Even <a
2181href="#Instruction"><tt>Instruction</tt></a>s and <a
2182href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
2183
2184<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
2185for a program. For example, an incoming argument to a function (represented
2186with an instance of the <a href="#Argument">Argument</a> class) is "used" by
2187every instruction in the function that references the argument. To keep track
2188of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
2189href="#User"><tt>User</tt></a>s that is using it (the <a
2190href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
2191graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
2192def-use information in the program, and is accessible through the <tt>use_</tt>*
2193methods, shown below.</p>
2194
2195<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
2196and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
2197method. In addition, all LLVM values can be named. The "name" of the
2198<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
2199
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2200<div class="doc_code">
2201<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2202%<b>foo</b> = add i32 1, 2
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2203</pre>
2204</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2205
2206<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
2207that the name of any value may be missing (an empty string), so names should
2208<b>ONLY</b> be used for debugging (making the source code easier to read,
2209debugging printouts), they should not be used to keep track of values or map
2210between them. For this purpose, use a <tt>std::map</tt> of pointers to the
2211<tt>Value</tt> itself instead.</p>
2212
2213<p>One important aspect of LLVM is that there is no distinction between an SSA
2214variable and the operation that produces it. Because of this, any reference to
2215the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]2216argument, for example) is represented as a direct pointer to the instance of
2217the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2218represents this value. Although this may take some getting used to, it
2219simplifies the representation and makes it easier to manipulate.</p>
2220
2221</div>
2222
2223<!-- _______________________________________________________________________ -->
2224<div class="doc_subsubsection">
2225 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
2226</div>
2227
2228<div class="doc_text">
2229
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2230<ul>
2231 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
2232use-list<br>
2233 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
2234the use-list<br>
2235 <tt>unsigned use_size()</tt> - Returns the number of users of the
2236value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2237 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2238 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
2239the use-list.<br>
2240 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
2241use-list.<br>
2242 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
2243element in the list.
2244 <p> These methods are the interface to access the def-use
2245information in LLVM. As with all other iterators in LLVM, the naming
2246conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2247 </li>
2248 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2249 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2250 </li>
2251 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2252 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2253 <tt>void setName(const std::string &amp;Name)</tt>
2254 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
2255be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2256 </li>
2257 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2258
2259 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
2260 href="#User"><tt>User</tt>s</a> of the current value to refer to
2261 "<tt>V</tt>" instead. For example, if you detect that an instruction always
2262 produces a constant value (for example through constant folding), you can
2263 replace all uses of the instruction with the constant like this:</p>
2264
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2265<div class="doc_code">
2266<pre>
2267Inst-&gt;replaceAllUsesWith(ConstVal);
2268</pre>
2269</div>
2270
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2271</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2272
2273</div>
2274
2275<!-- ======================================================================= -->
2276<div class="doc_subsection">
2277 <a name="User">The <tt>User</tt> class</a>
2278</div>
2279
2280<div class="doc_text">
2281
2282<p>
2283<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]2284doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2285Superclass: <a href="#Value"><tt>Value</tt></a></p>
2286
2287<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
2288refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
2289that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
2290referring to. The <tt>User</tt> class itself is a subclass of
2291<tt>Value</tt>.</p>
2292
2293<p>The operands of a <tt>User</tt> point directly to the LLVM <a
2294href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
2295Single Assignment (SSA) form, there can only be one definition referred to,
2296allowing this direct connection. This connection provides the use-def
2297information in LLVM.</p>
2298
2299</div>
2300
2301<!-- _______________________________________________________________________ -->
2302<div class="doc_subsubsection">
2303 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
2304</div>
2305
2306<div class="doc_text">
2307
2308<p>The <tt>User</tt> class exposes the operand list in two ways: through
2309an index access interface and through an iterator based interface.</p>
2310
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2311<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2312 <li><tt>Value *getOperand(unsigned i)</tt><br>
2313 <tt>unsigned getNumOperands()</tt>
2314 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2315convenient form for direct access.</p></li>
2316
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2317 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
2318list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2319 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
2320the operand list.<br>
2321 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2322operand list.
2323 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2324the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2325</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2326
2327</div>
2328
2329<!-- ======================================================================= -->
2330<div class="doc_subsection">
2331 <a name="Instruction">The <tt>Instruction</tt> class</a>
2332</div>
2333
2334<div class="doc_text">
2335
2336<p><tt>#include "</tt><tt><a
2337href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2338doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2339Superclasses: <a href="#User"><tt>User</tt></a>, <a
2340href="#Value"><tt>Value</tt></a></p>
2341
2342<p>The <tt>Instruction</tt> class is the common base class for all LLVM
2343instructions. It provides only a few methods, but is a very commonly used
2344class. The primary data tracked by the <tt>Instruction</tt> class itself is the
2345opcode (instruction type) and the parent <a
2346href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
2347into. To represent a specific type of instruction, one of many subclasses of
2348<tt>Instruction</tt> are used.</p>
2349
2350<p> Because the <tt>Instruction</tt> class subclasses the <a
2351href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
2352way as for other <a href="#User"><tt>User</tt></a>s (with the
2353<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
2354<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
2355the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
2356file contains some meta-data about the various different types of instructions
2357in LLVM. It describes the enum values that are used as opcodes (for example
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]2358<tt>Instruction::Add</tt> and <tt>Instruction::ICmp</tt>), as well as the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2359concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
2360example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]2361href="#CmpInst">CmpInst</a></tt>). Unfortunately, the use of macros in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2362this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2363<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2364
2365</div>
2366
2367<!-- _______________________________________________________________________ -->
2368<div class="doc_subsubsection">
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]2369 <a name="s_Instruction">Important Subclasses of the <tt>Instruction</tt>
2370 class</a>
2371</div>
2372<div class="doc_text">
2373 <ul>
2374 <li><tt><a name="BinaryOperator">BinaryOperator</a></tt>
2375 <p>This subclasses represents all two operand instructions whose operands
2376 must be the same type, except for the comparison instructions.</p></li>
2377 <li><tt><a name="CastInst">CastInst</a></tt>
2378 <p>This subclass is the parent of the 12 casting instructions. It provides
2379 common operations on cast instructions.</p>
2380 <li><tt><a name="CmpInst">CmpInst</a></tt>
2381 <p>This subclass respresents the two comparison instructions,
2382 <a href="LangRef.html#i_icmp">ICmpInst</a> (integer opreands), and
2383 <a href="LangRef.html#i_fcmp">FCmpInst</a> (floating point operands).</p>
2384 <li><tt><a name="TerminatorInst">TerminatorInst</a></tt>
2385 <p>This subclass is the parent of all terminator instructions (those which
2386 can terminate a block).</p>
2387 </ul>
2388 </div>
2389
2390<!-- _______________________________________________________________________ -->
2391<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2392 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
2393 class</a>
2394</div>
2395
2396<div class="doc_text">
2397
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2398<ul>
2399 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2400 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
2401this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2402 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2403 <p>Returns true if the instruction writes to memory, i.e. it is a
2404 <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]2405 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2406 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2407 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2408 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2409in all ways to the original except that the instruction has no parent
2410(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2411and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2412</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2413
2414</div>
2415
2416<!-- ======================================================================= -->
2417<div class="doc_subsection">
2418 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
2419</div>
2420
2421<div class="doc_text">
2422
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2423<p><tt>#include "<a
2424href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
2425doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
2426Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2427Superclass: <a href="#Value"><tt>Value</tt></a></p>
2428
2429<p>This class represents a single entry multiple exit section of the code,
2430commonly known as a basic block by the compiler community. The
2431<tt>BasicBlock</tt> class maintains a list of <a
2432href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
2433Matching the language definition, the last element of this list of instructions
2434is always a terminator instruction (a subclass of the <a
2435href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
2436
2437<p>In addition to tracking the list of instructions that make up the block, the
2438<tt>BasicBlock</tt> class also keeps track of the <a
2439href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
2440
2441<p>Note that <tt>BasicBlock</tt>s themselves are <a
2442href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
2443like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
2444<tt>label</tt>.</p>
2445
2446</div>
2447
2448<!-- _______________________________________________________________________ -->
2449<div class="doc_subsubsection">
2450 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
2451 class</a>
2452</div>
2453
2454<div class="doc_text">
2455
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2456<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2457
2458<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2459 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2460
2461<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
2462insertion into a function. The constructor optionally takes a name for the new
2463block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
2464the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
2465automatically inserted at the end of the specified <a
2466href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
2467manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
2468
2469<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
2470<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
2471<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2472<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2473STL-style functions for accessing the instruction list.
2474
2475<p>These methods and typedefs are forwarding functions that have the same
2476semantics as the standard library methods of the same names. These methods
2477expose the underlying instruction list of a basic block in a way that is easy to
2478manipulate. To get the full complement of container operations (including
2479operations to update the list), you must use the <tt>getInstList()</tt>
2480method.</p></li>
2481
2482<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
2483
2484<p>This method is used to get access to the underlying container that actually
2485holds the Instructions. This method must be used when there isn't a forwarding
2486function in the <tt>BasicBlock</tt> class for the operation that you would like
2487to perform. Because there are no forwarding functions for "updating"
2488operations, you need to use this if you want to update the contents of a
2489<tt>BasicBlock</tt>.</p></li>
2490
2491<li><tt><a href="#Function">Function</a> *getParent()</tt>
2492
2493<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
2494embedded into, or a null pointer if it is homeless.</p></li>
2495
2496<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
2497
2498<p> Returns a pointer to the terminator instruction that appears at the end of
2499the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
2500instruction in the block is not a terminator, then a null pointer is
2501returned.</p></li>
2502
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2503</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2504
2505</div>
2506
2507<!-- ======================================================================= -->
2508<div class="doc_subsection">
2509 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
2510</div>
2511
2512<div class="doc_text">
2513
2514<p><tt>#include "<a
2515href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2516doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
2517Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2518Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
2519<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]2520
2521<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
2522href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
2523visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
2524Because they are visible at global scope, they are also subject to linking with
2525other globals defined in different translation units. To control the linking
2526process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
2527<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2528defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2529
2530<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
2531<tt>static</tt> in C), it is not visible to code outside the current translation
2532unit, and does not participate in linking. If it has external linkage, it is
2533visible to external code, and does participate in linking. In addition to
2534linkage information, <tt>GlobalValue</tt>s keep track of which <a
2535href="#Module"><tt>Module</tt></a> they are currently part of.</p>
2536
2537<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
2538by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
2539global is always a pointer to its contents. It is important to remember this
2540when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
2541be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
2542subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2543i32]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2544the address of the first element of this array and the value of the
2545<tt>GlobalVariable</tt> are the same, they have different types. The
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2546<tt>GlobalVariable</tt>'s type is <tt>[24 x i32]</tt>. The first element's type
2547is <tt>i32.</tt> Because of this, accessing a global value requires you to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2548dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
2549can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
2550Language Reference Manual</a>.</p>
2551
2552</div>
2553
2554<!-- _______________________________________________________________________ -->
2555<div class="doc_subsubsection">
2556 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
2557 class</a>
2558</div>
2559
2560<div class="doc_text">
2561
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2562<ul>
2563 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2564 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2565 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
2566 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
2567 <p> </p>
2568 </li>
2569 <li><tt><a href="#Module">Module</a> *getParent()</tt>
2570 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2571GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2572</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2573
2574</div>
2575
2576<!-- ======================================================================= -->
2577<div class="doc_subsection">
2578 <a name="Function">The <tt>Function</tt> class</a>
2579</div>
2580
2581<div class="doc_text">
2582
2583<p><tt>#include "<a
2584href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2585info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2586Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2587<a href="#Constant"><tt>Constant</tt></a>,
2588<a href="#User"><tt>User</tt></a>,
2589<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2590
2591<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
2592actually one of the more complex classes in the LLVM heirarchy because it must
2593keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2594of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
2595<a href="#Argument"><tt>Argument</tt></a>s, and a
2596<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2597
2598<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
2599commonly used part of <tt>Function</tt> objects. The list imposes an implicit
2600ordering of the blocks in the function, which indicate how the code will be
2601layed out by the backend. Additionally, the first <a
2602href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
2603<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
2604block. There are no implicit exit nodes, and in fact there may be multiple exit
2605nodes from a single <tt>Function</tt>. If the <a
2606href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
2607the <tt>Function</tt> is actually a function declaration: the actual body of the
2608function hasn't been linked in yet.</p>
2609
2610<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
2611<tt>Function</tt> class also keeps track of the list of formal <a
2612href="#Argument"><tt>Argument</tt></a>s that the function receives. This
2613container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
2614nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
2615the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
2616
2617<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
2618LLVM feature that is only used when you have to look up a value by name. Aside
2619from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
2620internally to make sure that there are not conflicts between the names of <a
2621href="#Instruction"><tt>Instruction</tt></a>s, <a
2622href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
2623href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
2624
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2625<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
2626and therefore also a <a href="#Constant">Constant</a>. The value of the function
2627is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2628</div>
2629
2630<!-- _______________________________________________________________________ -->
2631<div class="doc_subsubsection">
2632 <a name="m_Function">Important Public Members of the <tt>Function</tt>
2633 class</a>
2634</div>
2635
2636<div class="doc_text">
2637
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2638<ul>
2639 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2640 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2641
2642 <p>Constructor used when you need to create new <tt>Function</tt>s to add
2643 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2644 create and what type of linkage the function should have. The <a
2645 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2646 specifies the formal arguments and return value for the function. The same
2647 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
2648 create multiple functions. The <tt>Parent</tt> argument specifies the Module
2649 in which the function is defined. If this argument is provided, the function
2650 will automatically be inserted into that module's list of
2651 functions.</p></li>
2652
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2653 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2654
2655 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
2656 function is "external", it does not have a body, and thus must be resolved
2657 by linking with a function defined in a different translation unit.</p></li>
2658
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2659 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2660 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2661
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2662 <tt>begin()</tt>, <tt>end()</tt>
2663 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2664
2665 <p>These are forwarding methods that make it easy to access the contents of
2666 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
2667 list.</p></li>
2668
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2669 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2670
2671 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
2672 is necessary to use when you need to update the list or perform a complex
2673 action that doesn't have a forwarding method.</p></li>
2674
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2675 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2676iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2677 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2678
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2679 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2680 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2681
2682 <p>These are forwarding methods that make it easy to access the contents of
2683 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
2684 list.</p></li>
2685
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2686 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2687
2688 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
2689 necessary to use when you need to update the list or perform a complex
2690 action that doesn't have a forwarding method.</p></li>
2691
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2692 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2693
2694 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
2695 function. Because the entry block for the function is always the first
2696 block, this returns the first block of the <tt>Function</tt>.</p></li>
2697
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2698 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
2699 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2700
2701 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
2702 <tt>Function</tt> and returns the return type of the function, or the <a
2703 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
2704 function.</p></li>
2705
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2706 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2707
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2708 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2709 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2710</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2711
2712</div>
2713
2714<!-- ======================================================================= -->
2715<div class="doc_subsection">
2716 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
2717</div>
2718
2719<div class="doc_text">
2720
2721<p><tt>#include "<a
2722href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
2723<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2724doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2725 Class</a><br>
2726Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2727<a href="#Constant"><tt>Constant</tt></a>,
2728<a href="#User"><tt>User</tt></a>,
2729<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2730
2731<p>Global variables are represented with the (suprise suprise)
2732<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
2733subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
2734always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2735"name" refers to their constant address). See
2736<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
2737variables may have an initial value (which must be a
2738<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
2739they may be marked as "constant" themselves (indicating that their contents
2740never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2741</div>
2742
2743<!-- _______________________________________________________________________ -->
2744<div class="doc_subsubsection">
2745 <a name="m_GlobalVariable">Important Public Members of the
2746 <tt>GlobalVariable</tt> class</a>
2747</div>
2748
2749<div class="doc_text">
2750
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2751<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2752 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
2753 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
2754 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
2755
2756 <p>Create a new global variable of the specified type. If
2757 <tt>isConstant</tt> is true then the global variable will be marked as
2758 unchanging for the program. The Linkage parameter specifies the type of
2759 linkage (internal, external, weak, linkonce, appending) for the variable. If
2760 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
2761 the resultant global variable will have internal linkage. AppendingLinkage
2762 concatenates together all instances (in different translation units) of the
2763 variable into a single variable but is only applicable to arrays. &nbsp;See
2764 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
2765 further details on linkage types. Optionally an initializer, a name, and the
2766 module to put the variable into may be specified for the global variable as
2767 well.</p></li>
2768
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2769 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2770
2771 <p>Returns true if this is a global variable that is known not to
2772 be modified at runtime.</p></li>
2773
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2774 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2775
2776 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
2777
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2778 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2779
2780 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
2781 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2782</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2783
2784</div>
2785
2786<!-- ======================================================================= -->
2787<div class="doc_subsection">
2788 <a name="Module">The <tt>Module</tt> class</a>
2789</div>
2790
2791<div class="doc_text">
2792
2793<p><tt>#include "<a
2794href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2795<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2796
2797<p>The <tt>Module</tt> class represents the top level structure present in LLVM
2798programs. An LLVM module is effectively either a translation unit of the
2799original program or a combination of several translation units merged by the
2800linker. The <tt>Module</tt> class keeps track of a list of <a
2801href="#Function"><tt>Function</tt></a>s, a list of <a
2802href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
2803href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
2804helpful member functions that try to make common operations easy.</p>
2805
2806</div>
2807
2808<!-- _______________________________________________________________________ -->
2809<div class="doc_subsubsection">
2810 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
2811</div>
2812
2813<div class="doc_text">
2814
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2815<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2816 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2817</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2818
2819<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
2820provide a name for it (probably based on the name of the translation unit).</p>
2821
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2822<ul>
2823 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]2824 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2825
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2826 <tt>begin()</tt>, <tt>end()</tt>
2827 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2828
2829 <p>These are forwarding methods that make it easy to access the contents of
2830 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
2831 list.</p></li>
2832
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2833 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2834
2835 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
2836 necessary to use when you need to update the list or perform a complex
2837 action that doesn't have a forwarding method.</p>
2838
2839 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2840</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2841
2842<hr>
2843
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2844<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2845 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2846
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2847 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2848
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2849 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2850 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2851
2852 <p> These are forwarding methods that make it easy to access the contents of
2853 a <tt>Module</tt> object's <a
2854 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
2855
2856 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
2857
2858 <p>Returns the list of <a
2859 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2860 use when you need to update the list or perform a complex action that
2861 doesn't have a forwarding method.</p>
2862
2863 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2864</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2865
2866<hr>
2867
2868<ul>
2869 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2870
2871 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2872 for this <tt>Module</tt>.</p>
2873
2874 <p><!-- Convenience methods --></p></li>
2875</ul>
2876
2877<hr>
2878
2879<ul>
2880 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2881 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2882
2883 <p>Look up the specified function in the <tt>Module</tt> <a
2884 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2885 <tt>null</tt>.</p></li>
2886
2887 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2888 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2889
2890 <p>Look up the specified function in the <tt>Module</tt> <a
2891 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2892 external declaration for the function and return it.</p></li>
2893
2894 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2895
2896 <p>If there is at least one entry in the <a
2897 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2898 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2899 string.</p></li>
2900
2901 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
2902 href="#Type">Type</a> *Ty)</tt>
2903
2904 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2905 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2906 name, true is returned and the <a
2907 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2908</ul>
2909
2910</div>
2911
2912<!-- ======================================================================= -->
2913<div class="doc_subsection">
2914 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2915</div>
2916
2917<div class="doc_text">
2918
2919<p>Constant represents a base class for different types of constants. It
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2920is subclassed by ConstantInt, ConstantArray, etc. for representing
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame]2921the various types of Constants.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2922
2923</div>
2924
2925<!-- _______________________________________________________________________ -->
2926<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2927 <a name="m_Constant">Important Public Methods</a>
2928</div>
2929<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2930</div>
2931
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2932<!-- _______________________________________________________________________ -->
2933<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2934<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2935<ul>
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2936 <li>ConstantInt : This subclass of Constant represents an integer constant of
2937 any width, including boolean (1 bit integer).
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2938 <ul>
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame]2939 <li><tt>int64_t getSExtValue() const</tt>: Returns the underlying value of
2940 this constant as a sign extended signed integer value.</li>
2941 <li><tt>uint64_t getZExtValue() const</tt>: Returns the underlying value
2942 of this constant as a zero extended unsigned integer value.</li>
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2943 <li><tt>static ConstantInt* get(const Type *Ty, uint64_t Val)</tt>:
2944 Returns the ConstantInt object that represents the value provided by
2945 <tt>Val</tt> for integer type <tt>Ty</tt>.</li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2946 </ul>
2947 </li>
2948 <li>ConstantFP : This class represents a floating point constant.
2949 <ul>
2950 <li><tt>double getValue() const</tt>: Returns the underlying value of
2951 this constant. </li>
2952 </ul>
2953 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2954 <li>ConstantArray : This represents a constant array.
2955 <ul>
2956 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2957 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2958 </ul>
2959 </li>
2960 <li>ConstantStruct : This represents a constant struct.
2961 <ul>
2962 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2963 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2964 </ul>
2965 </li>
2966 <li>GlobalValue : This represents either a global variable or a function. In
2967 either case, the value is a constant fixed address (after linking).
2968 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2969</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2970</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2971<!-- ======================================================================= -->
2972<div class="doc_subsection">
2973 <a name="Argument">The <tt>Argument</tt> class</a>
2974</div>
2975
2976<div class="doc_text">
2977
2978<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2979arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2980arguments. An argument has a pointer to the parent Function.</p>
2981
2982</div>
2983
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2984<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2985<hr>
2986<address>
2987 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
2988 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
2989 <a href="http://validator.w3.org/check/referer"><img
2990 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
2991
2992 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2993 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2994 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2995 Last modified: $Date$
2996</address>
2997
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2998</body>
2999</html>