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4<head>
5 <title>LLVM Programmer's Manual</title>
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Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]7</head>
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9
10<div class="doc_title">
11 LLVM Programmer's Manual
12</div>
13
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]14<ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]15 <li><a href="#introduction">Introduction</a></li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]16 <li><a href="#general">General Information</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]17 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]18 <li><a href="#stl">The C++ Standard Template Library</a></li>
19<!--
20 <li>The <tt>-time-passes</tt> option</li>
21 <li>How to use the LLVM Makefile system</li>
22 <li>How to write a regression test</li>
Chris Lattner61db4652004-12-08 19:05:44 +0000[diff] [blame]23
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]24-->
Chris Lattner84b7f8d2003-08-01 22:20:59 +0000[diff] [blame]25 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]26 </li>
27 <li><a href="#apis">Important and useful LLVM APIs</a>
28 <ul>
29 <li><a href="#isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt>
30and <tt>dyn_cast&lt;&gt;</tt> templates</a> </li>
31 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro &amp; <tt>-debug</tt>
32option</a>
33 <ul>
34 <li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
35and the <tt>-debug-only</tt> option</a> </li>
36 </ul>
37 </li>
38 <li><a href="#Statistic">The <tt>Statistic</tt> template &amp; <tt>-stats</tt>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]39option</a></li>
40<!--
41 <li>The <tt>InstVisitor</tt> template
42 <li>The general graph API
43-->
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]44 </ul>
45 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]46 <li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]47 <ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]48 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
49 <ul>
50 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
51in a <tt>Function</tt></a> </li>
52 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
53in a <tt>BasicBlock</tt></a> </li>
54 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
55in a <tt>Function</tt></a> </li>
56 <li><a href="#iterate_convert">Turning an iterator into a
57class pointer</a> </li>
58 <li><a href="#iterate_complex">Finding call sites: a more
59complex example</a> </li>
60 <li><a href="#calls_and_invokes">Treating calls and invokes
61the same way</a> </li>
62 <li><a href="#iterate_chains">Iterating over def-use &amp;
63use-def chains</a> </li>
64 </ul>
65 </li>
66 <li><a href="#simplechanges">Making simple changes</a>
67 <ul>
68 <li><a href="#schanges_creating">Creating and inserting new
69 <tt>Instruction</tt>s</a> </li>
70 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
71 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
72with another <tt>Value</tt></a> </li>
73 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]74 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]75<!--
76 <li>Working with the Control Flow Graph
77 <ul>
78 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
79 <li>
80 <li>
81 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]82-->
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]83 </ul>
84 </li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame^]85
86 <li><a href="#advanced">Advanced Topics</a>
87 <ul>
88 <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
89 </ul></li>
90
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]91 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]92 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]93 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]94 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]95 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]96 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]97 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
98 <ul>
99 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
100 </ul>
101 </li>
102 <li><a href="#Module">The <tt>Module</tt> class</a></li>
103 <li><a href="#Constant">The <tt>Constant</tt> class</a>
104 <ul>
105 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
106 <ul>
107 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
108 <li><a href="#Function">The <tt>Function</tt> class</a></li>
109 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
110 </ul>
111 </li>
112 </ul>
113 </li>
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]114 </ul>
115 </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]116 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]117 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]118 </ul>
119 </li>
120 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]121 </li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]122</ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]123
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]124<div class="doc_author">
125 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner94c43592004-05-26 16:52:55 +0000[diff] [blame]126 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
127 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
128 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]129</div>
130
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]131<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]132<div class="doc_section">
133 <a name="introduction">Introduction </a>
134</div>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]135<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]136
137<div class="doc_text">
138
139<p>This document is meant to highlight some of the important classes and
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]140interfaces available in the LLVM source-base. This manual is not
141intended to explain what LLVM is, how it works, and what LLVM code looks
142like. It assumes that you know the basics of LLVM and are interested
143in writing transformations or otherwise analyzing or manipulating the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]144code.</p>
145
146<p>This document should get you oriented so that you can find your
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]147way in the continuously growing source code that makes up the LLVM
148infrastructure. Note that this manual is not intended to serve as a
149replacement for reading the source code, so if you think there should be
150a method in one of these classes to do something, but it's not listed,
151check the source. Links to the <a href="/doxygen/">doxygen</a> sources
152are provided to make this as easy as possible.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]153
154<p>The first section of this document describes general information that is
155useful to know when working in the LLVM infrastructure, and the second describes
156the Core LLVM classes. In the future this manual will be extended with
157information describing how to use extension libraries, such as dominator
158information, CFG traversal routines, and useful utilities like the <tt><a
159href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
160
161</div>
162
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]163<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]164<div class="doc_section">
165 <a name="general">General Information</a>
166</div>
167<!-- *********************************************************************** -->
168
169<div class="doc_text">
170
171<p>This section contains general information that is useful if you are working
172in the LLVM source-base, but that isn't specific to any particular API.</p>
173
174</div>
175
176<!-- ======================================================================= -->
177<div class="doc_subsection">
178 <a name="stl">The C++ Standard Template Library</a>
179</div>
180
181<div class="doc_text">
182
183<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]184perhaps much more than you are used to, or have seen before. Because of
185this, you might want to do a little background reading in the
186techniques used and capabilities of the library. There are many good
187pages that discuss the STL, and several books on the subject that you
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]188can get, so it will not be discussed in this document.</p>
189
190<p>Here are some useful links:</p>
191
192<ol>
193
194<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
195reference</a> - an excellent reference for the STL and other parts of the
196standard C++ library.</li>
197
198<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]199O'Reilly book in the making. It has a decent
200Standard Library
201Reference 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]202published.</li>
203
204<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
205Questions</a></li>
206
207<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
208Contains a useful <a
209href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
210STL</a>.</li>
211
212<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
213Page</a></li>
214
Tanya Lattner79445ba2004-12-08 18:34:56 +0000[diff] [blame]215<li><a href="http://64.78.49.204/">
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]216Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
217the book).</a></li>
218
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]219</ol>
220
221<p>You are also encouraged to take a look at the <a
222href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
223to write maintainable code more than where to put your curly braces.</p>
224
225</div>
226
227<!-- ======================================================================= -->
228<div class="doc_subsection">
229 <a name="stl">Other useful references</a>
230</div>
231
232<div class="doc_text">
233
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]234<ol>
235<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]236Branch and Tag Primer</a></li>
Misha Brukmana0f71e42004-06-18 18:39:00 +0000[diff] [blame]237<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
238static and shared libraries across platforms</a></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]239</ol>
240
241</div>
242
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]243<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]244<div class="doc_section">
245 <a name="apis">Important and useful LLVM APIs</a>
246</div>
247<!-- *********************************************************************** -->
248
249<div class="doc_text">
250
251<p>Here we highlight some LLVM APIs that are generally useful and good to
252know about when writing transformations.</p>
253
254</div>
255
256<!-- ======================================================================= -->
257<div class="doc_subsection">
258 <a name="isa">The isa&lt;&gt;, cast&lt;&gt; and dyn_cast&lt;&gt; templates</a>
259</div>
260
261<div class="doc_text">
262
263<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]264These templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
265operator, but they don't have some drawbacks (primarily stemming from
266the fact that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that
267have a v-table). Because they are used so often, you must know what they
268do and how they work. All of these templates are defined in the <a
269 href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]270file (note that you very rarely have to include this file directly).</p>
271
272<dl>
273 <dt><tt>isa&lt;&gt;</tt>: </dt>
274
275 <dd>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
276 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
277 a reference or pointer points to an instance of the specified class. This can
278 be very useful for constraint checking of various sorts (example below).</dd>
279
280 <dt><tt>cast&lt;&gt;</tt>: </dt>
281
282 <dd>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
283 converts a pointer or reference from a base class to a derived cast, causing
284 an assertion failure if it is not really an instance of the right type. This
285 should be used in cases where you have some information that makes you believe
286 that something is of the right type. An example of the <tt>isa&lt;&gt;</tt>
287 and <tt>cast&lt;&gt;</tt> template is:
288
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]289 <pre>
290 static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
291 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))
292 return true;
293
Chris Lattner53f72b32005-04-22 04:49:59 +0000[diff] [blame]294 <i>// Otherwise, it must be an instruction...</i>
295 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
296 }
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]297 </pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]298
299 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
300 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
301 operator.</p>
302
303 </dd>
304
305 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
306
307 <dd>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation. It
308 checks to see if the operand is of the specified type, and if so, returns a
309 pointer to it (this operator does not work with references). If the operand is
310 not of the correct type, a null pointer is returned. Thus, this works very
311 much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
312 same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt> operator is used
313 in an <tt>if</tt> statement or some other flow control statement like this:
314
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]315 <pre>
316 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
317 ...
318 }
319 </pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]320
321 <p> This form of the <tt>if</tt> statement effectively combines together a
322 call to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
323 statement, which is very convenient.</p>
324
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]325 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
326 <tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
327 In particular you should not use big chained <tt>if/then/else</tt> blocks to
328 check for lots of different variants of classes. If you find yourself
329 wanting to do this, it is much cleaner and more efficient to use the
Chris Lattner53f72b32005-04-22 04:49:59 +0000[diff] [blame]330 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]331
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]332 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]333
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]334 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]335
336 <dd>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
337 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as
338 an argument (which it then propagates). This can sometimes be useful,
339 allowing you to combine several null checks into one.</dd>
340
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]341 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]342
343 <dd>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
344 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
345 as an argument (which it then propagates). This can sometimes be useful,
346 allowing you to combine several null checks into one.</dd>
347
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]348 </dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]349
350<p>These five templates can be used with any classes, whether they have a
351v-table or not. To add support for these templates, you simply need to add
352<tt>classof</tt> static methods to the class you are interested casting
353to. Describing this is currently outside the scope of this document, but there
354are lots of examples in the LLVM source base.</p>
355
356</div>
357
358<!-- ======================================================================= -->
359<div class="doc_subsection">
360 <a name="DEBUG">The <tt>DEBUG()</tt> macro &amp; <tt>-debug</tt> option</a>
361</div>
362
363<div class="doc_text">
364
365<p>Often when working on your pass you will put a bunch of debugging printouts
366and other code into your pass. After you get it working, you want to remove
367it... but you may need it again in the future (to work out new bugs that you run
368across).</p>
369
370<p> Naturally, because of this, you don't want to delete the debug printouts,
371but you don't want them to always be noisy. A standard compromise is to comment
372them out, allowing you to enable them if you need them in the future.</p>
373
374<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
375file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
376this problem. Basically, you can put arbitrary code into the argument of the
377<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
378tool) is run with the '<tt>-debug</tt>' command line argument:</p>
379
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]380 <pre> ... <br> DEBUG(std::cerr &lt;&lt; "I am here!\n");<br> ...<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]381
382<p>Then you can run your pass like this:</p>
383
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]384 <pre> $ opt &lt; a.bc &gt; /dev/null -mypass<br> &lt;no output&gt;<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug<br> I am here!<br> $<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]385
386<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
387to not have to create "yet another" command line option for the debug output for
388your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
389so they do not cause a performance impact at all (for the same reason, they
390should also not contain side-effects!).</p>
391
392<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
393enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
394"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
395program hasn't been started yet, you can always just run it with
396<tt>-debug</tt>.</p>
397
398</div>
399
400<!-- _______________________________________________________________________ -->
401<div class="doc_subsubsection">
402 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
403 the <tt>-debug-only</tt> option</a>
404</div>
405
406<div class="doc_text">
407
408<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
409just turns on <b>too much</b> information (such as when working on the code
410generator). If you want to enable debug information with more fine-grained
411control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
412option as follows:</p>
413
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]414 <pre> ...<br> DEBUG(std::cerr &lt;&lt; "No debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "foo"<br> DEBUG(std::cerr &lt;&lt; "'foo' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "bar"<br> DEBUG(std::cerr &lt;&lt; "'bar' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE ""<br> DEBUG(std::cerr &lt;&lt; "No debug type (2)\n");<br> ...<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]415
416<p>Then you can run your pass like this:</p>
417
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]418 <pre> $ opt &lt; a.bc &gt; /dev/null -mypass<br> &lt;no output&gt;<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug<br> No debug type<br> 'foo' debug type<br> 'bar' debug type<br> No debug type (2)<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo<br> 'foo' debug type<br> $ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar<br> 'bar' debug type<br> $<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]419
420<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
421a file, to specify the debug type for the entire module (if you do this before
422you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
423<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
424"bar", because there is no system in place to ensure that names do not
425conflict. If two different modules use the same string, they will all be turned
426on when the name is specified. This allows, for example, all debug information
427for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]428even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]429
430</div>
431
432<!-- ======================================================================= -->
433<div class="doc_subsection">
434 <a name="Statistic">The <tt>Statistic</tt> template &amp; <tt>-stats</tt>
435 option</a>
436</div>
437
438<div class="doc_text">
439
440<p>The "<tt><a
441href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
442provides a template named <tt>Statistic</tt> that is used as a unified way to
443keep track of what the LLVM compiler is doing and how effective various
444optimizations are. It is useful to see what optimizations are contributing to
445making a particular program run faster.</p>
446
447<p>Often you may run your pass on some big program, and you're interested to see
448how many times it makes a certain transformation. Although you can do this with
449hand inspection, or some ad-hoc method, this is a real pain and not very useful
450for big programs. Using the <tt>Statistic</tt> template makes it very easy to
451keep track of this information, and the calculated information is presented in a
452uniform manner with the rest of the passes being executed.</p>
453
454<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
455it are as follows:</p>
456
457<ol>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]458 <li>Define your statistic like this:
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]459 <pre>static Statistic&lt;&gt; NumXForms("mypassname", "The # of times I did stuff");<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]460
461 <p>The <tt>Statistic</tt> template can emulate just about any data-type,
462 but if you do not specify a template argument, it defaults to acting like
463 an unsigned int counter (this is usually what you want).</p></li>
464
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]465 <li>Whenever you make a transformation, bump the counter:
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]466 <pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]467 </li>
468 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]469
470 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
471 statistics gathered, use the '<tt>-stats</tt>' option:</p>
472
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]473 <pre> $ opt -stats -mypassname &lt; program.bc &gt; /dev/null<br> ... statistic output ...<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]474
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]475 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
476suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]477
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]478 <pre> 7646 bytecodewriter - Number of normal instructions<br> 725 bytecodewriter - Number of oversized instructions<br> 129996 bytecodewriter - Number of bytecode bytes written<br> 2817 raise - Number of insts DCEd or constprop'd<br> 3213 raise - Number of cast-of-self removed<br> 5046 raise - Number of expression trees converted<br> 75 raise - Number of other getelementptr's formed<br> 138 raise - Number of load/store peepholes<br> 42 deadtypeelim - Number of unused typenames removed from symtab<br> 392 funcresolve - Number of varargs functions resolved<br> 27 globaldce - Number of global variables removed<br> 2 adce - Number of basic blocks removed<br> 134 cee - Number of branches revectored<br> 49 cee - Number of setcc instruction eliminated<br> 532 gcse - Number of loads removed<br> 2919 gcse - Number of instructions removed<br> 86 indvars - Number of canonical indvars added<br> 87 indvars - Number of aux indvars removed<br> 25 instcombine - Number of dead inst eliminate<br> 434 instcombine - Number of insts combined<br> 248 licm - Number of load insts hoisted<br> 1298 licm - Number of insts hoisted to a loop pre-header<br> 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)<br> 75 mem2reg - Number of alloca's promoted<br> 1444 cfgsimplify - Number of blocks simplified<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]479
480<p>Obviously, with so many optimizations, having a unified framework for this
481stuff is very nice. Making your pass fit well into the framework makes it more
482maintainable and useful.</p>
483
484</div>
485
486<!-- *********************************************************************** -->
487<div class="doc_section">
488 <a name="common">Helpful Hints for Common Operations</a>
489</div>
490<!-- *********************************************************************** -->
491
492<div class="doc_text">
493
494<p>This section describes how to perform some very simple transformations of
495LLVM code. This is meant to give examples of common idioms used, showing the
496practical side of LLVM transformations. <p> Because this is a "how-to" section,
497you should also read about the main classes that you will be working with. The
498<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
499and descriptions of the main classes that you should know about.</p>
500
501</div>
502
503<!-- NOTE: this section should be heavy on example code -->
504<!-- ======================================================================= -->
505<div class="doc_subsection">
506 <a name="inspection">Basic Inspection and Traversal Routines</a>
507</div>
508
509<div class="doc_text">
510
511<p>The LLVM compiler infrastructure have many different data structures that may
512be traversed. Following the example of the C++ standard template library, the
513techniques used to traverse these various data structures are all basically the
514same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
515method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
516function returns an iterator pointing to one past the last valid element of the
517sequence, and there is some <tt>XXXiterator</tt> data type that is common
518between the two operations.</p>
519
520<p>Because the pattern for iteration is common across many different aspects of
521the program representation, the standard template library algorithms may be used
522on them, and it is easier to remember how to iterate. First we show a few common
523examples of the data structures that need to be traversed. Other data
524structures are traversed in very similar ways.</p>
525
526</div>
527
528<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]529<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]530 <a name="iterate_function">Iterating over the </a><a
531 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
532 href="#Function"><tt>Function</tt></a>
533</div>
534
535<div class="doc_text">
536
537<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
538transform in some way; in particular, you'd like to manipulate its
539<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
540the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
541an example that prints the name of a <tt>BasicBlock</tt> and the number of
542<tt>Instruction</tt>s it contains:</p>
543
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]544 <pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> cerr &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has " <br> &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";<br> }<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]545
546<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]547invoking member functions of the <tt>Instruction</tt> class. This is
548because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]549classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]550exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
551
552</div>
553
554<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]555<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]556 <a name="iterate_basicblock">Iterating over the </a><a
557 href="#Instruction"><tt>Instruction</tt></a>s in a <a
558 href="#BasicBlock"><tt>BasicBlock</tt></a>
559</div>
560
561<div class="doc_text">
562
563<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
564easy to iterate over the individual instructions that make up
565<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
566a <tt>BasicBlock</tt>:</p>
567
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]568<pre>
569 // blk is a pointer to a BasicBlock instance
570 for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
571 // the next statement works since operator&lt;&lt;(ostream&amp;,...)
572 // is overloaded for Instruction&amp;
573 std::cerr &lt;&lt; *i &lt;&lt; "\n";
574</pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]575
576<p>However, this isn't really the best way to print out the contents of a
577<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
578anything you'll care about, you could have just invoked the print routine on the
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]579basic block itself: <tt>std::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]580
581</div>
582
583<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]584<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]585 <a name="iterate_institer">Iterating over the </a><a
586 href="#Instruction"><tt>Instruction</tt></a>s in a <a
587 href="#Function"><tt>Function</tt></a>
588</div>
589
590<div class="doc_text">
591
592<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
593<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
594<tt>InstIterator</tt> should be used instead. You'll need to include <a
595href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
596and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]597small 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]598
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]599 <pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> cerr &lt;&lt; *i &lt;&lt; "\n";<br></pre>
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]600Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
601worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]602initialize a worklist to contain all instructions in a <tt>Function</tt>
603F, all you would need to do is something like:
604 <pre>std::set&lt;Instruction*&gt; worklist;<br>worklist.insert(inst_begin(F), inst_end(F));<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]605
606<p>The STL set <tt>worklist</tt> would now contain all instructions in the
607<tt>Function</tt> pointed to by F.</p>
608
609</div>
610
611<!-- _______________________________________________________________________ -->
612<div class="doc_subsubsection">
613 <a name="iterate_convert">Turning an iterator into a class pointer (and
614 vice-versa)</a>
615</div>
616
617<div class="doc_text">
618
619<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]620instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]621a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]622Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]623is a <tt>BasicBlock::const_iterator</tt>:</p>
624
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]625 <pre> Instruction&amp; inst = *i; // grab reference to instruction reference<br> Instruction* pinst = &amp;*i; // grab pointer to instruction reference<br> const Instruction&amp; inst = *j;<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]626
627<p>However, the iterators you'll be working with in the LLVM framework are
628special: they will automatically convert to a ptr-to-instance type whenever they
629need to. Instead of dereferencing the iterator and then taking the address of
630the result, you can simply assign the iterator to the proper pointer type and
631you get the dereference and address-of operation as a result of the assignment
632(behind the scenes, this is a result of overloading casting mechanisms). Thus
633the last line of the last example,</p>
634
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]635 <pre>Instruction* pinst = &amp;*i;</pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]636
637<p>is semantically equivalent to</p>
638
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]639 <pre>Instruction* pinst = i;</pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]640
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]641<p>It's also possible to turn a class pointer into the corresponding iterator,
642and this is a constant time operation (very efficient). The following code
643snippet illustrates use of the conversion constructors provided by LLVM
644iterators. By using these, you can explicitly grab the iterator of something
645without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]646
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]647 <pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after *inst.<br> if (it != inst-&gt;getParent()-&gt;end()) cerr &lt;&lt; *it &lt;&lt; "\n";<br>}<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]648
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]649</div>
650
651<!--_______________________________________________________________________-->
652<div class="doc_subsubsection">
653 <a name="iterate_complex">Finding call sites: a slightly more complex
654 example</a>
655</div>
656
657<div class="doc_text">
658
659<p>Say that you're writing a FunctionPass and would like to count all the
660locations in the entire module (that is, across every <tt>Function</tt>) where a
661certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
662learn 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]663much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]664you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
665is what we want to do:</p>
666
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]667 <pre>initialize callCounter to zero<br>for each Function f in the Module<br> for each BasicBlock b in f<br> for each Instruction i in b<br> if (i is a CallInst and calls the given function)<br> increment callCounter<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]668
669<p>And the actual code is (remember, since we're writing a
670<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
671override the <tt>runOnFunction</tt> method...):</p>
672
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]673 <pre>Function* targetFunc = ...;<br><br>class OurFunctionPass : public FunctionPass {<br> public:<br> OurFunctionPass(): callCounter(0) { }<br><br> virtual runOnFunction(Function&amp; F) {<br> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {<br> for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {<br> if (<a
674 href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
675 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {<br> // we know we've encountered a call instruction, so we<br> // need to determine if it's a call to the<br> // function pointed to by m_func or not.<br> <br> if (callInst-&gt;getCalledFunction() == targetFunc)<br> ++callCounter;<br> }<br> }<br> }<br> <br> private:<br> unsigned callCounter;<br>};<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]676
677</div>
678
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]679<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]680<div class="doc_subsubsection">
681 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
682</div>
683
684<div class="doc_text">
685
686<p>You may have noticed that the previous example was a bit oversimplified in
687that it did not deal with call sites generated by 'invoke' instructions. In
688this, and in other situations, you may find that you want to treat
689<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
690most-specific common base class is <tt>Instruction</tt>, which includes lots of
691less closely-related things. For these cases, LLVM provides a handy wrapper
692class called <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]693href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]694It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
695methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]696<tt>InvokeInst</tt>s.</p>
697
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]698<p>This class has "value semantics": it should be passed by value, not by
699reference and it should not be dynamically allocated or deallocated using
700<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
701assignable and constructable, with costs equivalents to that of a bare pointer.
702If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]703
704</div>
705
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]706<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]707<div class="doc_subsubsection">
708 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
709</div>
710
711<div class="doc_text">
712
713<p>Frequently, we might have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]714href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
715determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
716<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
717For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
718particular function <tt>foo</tt>. Finding all of the instructions that
719<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
720of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]721
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]722 <pre>Function* F = ...;<br><br>for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i) {<br> if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {<br> cerr &lt;&lt; "F is used in instruction:\n";<br> cerr &lt;&lt; *Inst &lt;&lt; "\n";<br> }<br>}<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]723
724<p>Alternately, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]725href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]726<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
727<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
728<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
729all of the values that a particular instruction uses (that is, the operands of
730the particular <tt>Instruction</tt>):</p>
731
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]732 <pre>Instruction* pi = ...;<br><br>for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {<br> Value* v = *i;<br> ...<br>}<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]733
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]734<!--
735 def-use chains ("finding all users of"): Value::use_begin/use_end
736 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]737-->
738
739</div>
740
741<!-- ======================================================================= -->
742<div class="doc_subsection">
743 <a name="simplechanges">Making simple changes</a>
744</div>
745
746<div class="doc_text">
747
748<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]749infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]750transformations, it's fairly common to manipulate the contents of basic
751blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]752and gives example code.</p>
753
754</div>
755
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]756<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]757<div class="doc_subsubsection">
758 <a name="schanges_creating">Creating and inserting new
759 <tt>Instruction</tt>s</a>
760</div>
761
762<div class="doc_text">
763
764<p><i>Instantiating Instructions</i></p>
765
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]766<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]767constructor for the kind of instruction to instantiate and provide the necessary
768parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
769(const-ptr-to) <tt>Type</tt>. Thus:</p>
770
771<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
772
773<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
774one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
775subclass is likely to have varying default parameters which change the semantics
776of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]777href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]778Instruction</a> that you're interested in instantiating.</p>
779
780<p><i>Naming values</i></p>
781
782<p>It is very useful to name the values of instructions when you're able to, as
783this facilitates the debugging of your transformations. If you end up looking
784at generated LLVM machine code, you definitely want to have logical names
785associated with the results of instructions! By supplying a value for the
786<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
787associate a logical name with the result of the instruction's execution at
788runtime. For example, say that I'm writing a transformation that dynamically
789allocates space for an integer on the stack, and that integer is going to be
790used as some kind of index by some other code. To accomplish this, I place an
791<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
792<tt>Function</tt>, and I'm intending to use it within the same
793<tt>Function</tt>. I might do:</p>
794
795 <pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
796
797<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
798execution value, which is a pointer to an integer on the runtime stack.</p>
799
800<p><i>Inserting instructions</i></p>
801
802<p>There are essentially two ways to insert an <tt>Instruction</tt>
803into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
804
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]805<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]806 <li>Insertion into an explicit instruction list
807
808 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
809 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
810 before <tt>*pi</tt>, we do the following: </p>
811
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]812 <pre> BasicBlock *pb = ...;<br> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb-&gt;getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre>
813
814 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
815 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
816 classes provide constructors which take a pointer to a
817 <tt>BasicBlock</tt> to be appended to. For example code that
818 looked like: </p>
819
820 <pre> BasicBlock *pb = ...;<br> Instruction *newInst = new Instruction(...);<br> pb-&gt;getInstList().push_back(newInst); // appends newInst to pb<br></pre>
821
822 <p>becomes: </p>
823
824 <pre> BasicBlock *pb = ...;<br> Instruction *newInst = new Instruction(..., pb);<br></pre>
825
826 <p>which is much cleaner, especially if you are creating
827 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]828
829 <li>Insertion into an implicit instruction list
830
831 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
832 are implicitly associated with an existing instruction list: the instruction
833 list of the enclosing basic block. Thus, we could have accomplished the same
834 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
835 </p>
836
837 <pre> Instruction *pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);<br></pre>
838
839 <p>In fact, this sequence of steps occurs so frequently that the
840 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
841 constructors which take (as a default parameter) a pointer to an
842 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
843 precede. That is, <tt>Instruction</tt> constructors are capable of
844 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
845 provided instruction, immediately before that instruction. Using an
846 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
847 parameter, the above code becomes:</p>
848
849 <pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
850
851 <p>which is much cleaner, especially if you're creating a lot of
852instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
853</ul>
854
855</div>
856
857<!--_______________________________________________________________________-->
858<div class="doc_subsubsection">
859 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
860</div>
861
862<div class="doc_text">
863
864<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]865<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]866you must have a pointer to the instruction that you wish to delete. Second, you
867need to obtain the pointer to that instruction's basic block. You use the
868pointer to the basic block to get its list of instructions and then use the
869erase function to remove your instruction. For example:</p>
870
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]871 <pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
872 href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();<br> BB-&gt;getInstList().erase(I);<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]873
874</div>
875
876<!--_______________________________________________________________________-->
877<div class="doc_subsubsection">
878 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
879 <tt>Value</tt></a>
880</div>
881
882<div class="doc_text">
883
884<p><i>Replacing individual instructions</i></p>
885
886<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]887permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]888and <tt>ReplaceInstWithInst</tt>.</p>
889
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]890<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]891
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]892<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]893 <li><tt>ReplaceInstWithValue</tt>
894
895 <p>This function replaces all uses (within a basic block) of a given
896 instruction with a value, and then removes the original instruction. The
897 following example illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]898 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]899 pointer to an integer.</p>
900
901 <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
902
903 <li><tt>ReplaceInstWithInst</tt>
904
905 <p>This function replaces a particular instruction with another
906 instruction. The following example illustrates the replacement of one
907 <tt>AllocaInst</tt> with another.</p>
908
909 <pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,<br> new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));<br></pre></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]910</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]911
912<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
913
914<p>You can use <tt>Value::replaceAllUsesWith</tt> and
915<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]916doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
917and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]918information.</p>
919
920<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
921include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
922ReplaceInstWithValue, ReplaceInstWithInst -->
923
924</div>
925
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]926<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]927<div class="doc_section">
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame^]928 <a name="advanced">Advanced Topics</a>
929</div>
930<!-- *********************************************************************** -->
931
932<div class="doc_text">
933
934
935</div>
936
937
938<!-- ======================================================================= -->
939<div class="doc_subsection">
940 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
941</div>
942<div class="doc_text">
943<p>This class provides a symbol table that the <a
944href="#Function"><tt>Function</tt></a> and <a href="#Module">
945<tt>Module</tt></a> classes use for naming definitions. The symbol table can
946provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
947href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
948type. It hides the data it contains and provides access to it through a
949controlled interface.</p>
950
951<p>Note that the symbol table class is should not be directly accessed by most
952clients. It should only be used when iteration over the symbol table names
953themselves are required, which is very special purpose. Note that not all LLVM
954<a href="#Value">Value</a>s have names, and those without names (i.e. they have
955an empty name) do not exist in the symbol table.
956</p>
957
958<p>To use the <tt>SymbolTable</tt> well, you need to understand the
959structure of the information it holds. The class contains two
960<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
961<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
962The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
963are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
964however, are stored in a single dimension and accessed only by name.</p>
965
966<p>The interface of this class provides three basic types of operations:
967<ol>
968 <li><em>Accessors</em>. Accessors provide read-only access to information
969 such as finding a value for a name with the
970 <a href="#SymbolTable_lookup">lookup</a> method.</li>
971 <li><em>Mutators</em>. Mutators allow the user to add information to the
972 <tt>SymbolTable</tt> with methods like
973 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
974 <li><em>Iterators</em>. Iterators allow the user to traverse the content
975 of the symbol table in well defined ways, such as the method
976 <a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
977</ol>
978
979<h3>Accessors</h3>
980<dl>
981 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
982 </dt>
983 <dd>The <tt>lookup</tt> method searches the type plane given by the
984 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
985 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
986
987 <dt><tt>Type* lookupType( const std::string&amp; name) const</tt>:</dt>
988 <dd>The <tt>lookupType</tt> method searches through the types for a
989 <tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
990 is not found, null is returned.</dd>
991
992 <dt><tt>bool hasTypes() const</tt>:</dt>
993 <dd>This function returns true if an entry has been made into the type
994 map.</dd>
995
996 <dt><tt>bool isEmpty() const</tt>:</dt>
997 <dd>This function returns true if both the value and types maps are
998 empty</dd>
999</dl>
1000
1001<h3>Mutators</h3>
1002<dl>
1003 <dt><tt>void insert(Value *Val)</tt>:</dt>
1004 <dd>This method adds the provided value to the symbol table. The Value must
1005 have both a name and a type which are extracted and used to place the value
1006 in the correct type plane under the value's name.</dd>
1007
1008 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1009 <dd> Inserts a constant or type into the symbol table with the specified
1010 name. There can be a many to one mapping between names and constants
1011 or types.</dd>
1012
1013 <dt><tt>void insert(const std::string&amp; Name, Type *Typ)</tt>:</dt>
1014 <dd> Inserts a type into the symbol table with the specified name. There
1015 can be a many-to-one mapping between names and types. This method
1016 allows a type with an existing entry in the symbol table to get
1017 a new name.</dd>
1018
1019 <dt><tt>void remove(Value* Val)</tt>:</dt>
1020 <dd> This method removes a named value from the symbol table. The
1021 type and name of the Value are extracted from \p N and used to
1022 lookup the Value in the correct type plane. If the Value is
1023 not in the symbol table, this method silently ignores the
1024 request.</dd>
1025
1026 <dt><tt>void remove(Type* Typ)</tt>:</dt>
1027 <dd> This method removes a named type from the symbol table. The
1028 name of the type is extracted from \P T and used to look up
1029 the Type in the type map. If the Type is not in the symbol
1030 table, this method silently ignores the request.</dd>
1031
1032 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1033 <dd> Remove a constant or type with the specified name from the
1034 symbol table.</dd>
1035
1036 <dt><tt>Type* remove(const std::string&amp; Name, Type* T)</tt>:</dt>
1037 <dd> Remove a type with the specified name from the symbol table.
1038 Returns the removed Type.</dd>
1039
1040 <dt><tt>Value *value_remove(const value_iterator&amp; It)</tt>:</dt>
1041 <dd> Removes a specific value from the symbol table.
1042 Returns the removed value.</dd>
1043
1044 <dt><tt>bool strip()</tt>:</dt>
1045 <dd> This method will strip the symbol table of its names leaving
1046 the type and values. </dd>
1047
1048 <dt><tt>void clear()</tt>:</dt>
1049 <dd>Empty the symbol table completely.</dd>
1050</dl>
1051
1052<h3>Iteration</h3>
1053<p>The following functions describe three types of iterators you can obtain
1054the beginning or end of the sequence for both const and non-const. It is
1055important to keep track of the different kinds of iterators. There are
1056three idioms worth pointing out:</p>
1057<table>
1058 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1059 <tr>
1060 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1061 <td align="left"><pre><tt>
1062for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1063 PE = ST.plane_end(); PI != PE; ++PI ) {
1064 PI-&gt;first // This is the Type* of the plane
1065 PI-&gt;second // This is the SymbolTable::ValueMap of name/Value pairs
1066 </tt></pre></td>
1067 </tr>
1068 <tr>
1069 <td align="left">All name/Type Pairs</td><td>TI</td>
1070 <td align="left"><pre><tt>
1071for (SymbolTable::type_const_iterator TI = ST.type_begin(),
1072 TE = ST.type_end(); TI != TE; ++TI )
1073 TI-&gt;first // This is the name of the type
1074 TI-&gt;second // This is the Type* value associated with the name
1075 </tt></pre></td>
1076 </tr>
1077 <tr>
1078 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1079 <td align="left"><pre><tt>
1080for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
1081 VE = ST.value_end(SomeType); VI != VE; ++VI )
1082 VI-&gt;first // This is the name of the Value
1083 VI-&gt;second // This is the Value* value associated with the name
1084 </tt></pre></td>
1085 </tr>
1086</table>
1087
1088<p>Using the recommended iterator names and idioms will help you avoid
1089making mistakes. Of particular note, make sure that whenever you use
1090value_begin(SomeType) that you always compare the resulting iterator
1091with value_end(SomeType) not value_end(SomeOtherType) or else you
1092will loop infinitely.</p>
1093
1094<dl>
1095
1096 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1097 <dd>Get an iterator that starts at the beginning of the type planes.
1098 The iterator will iterate over the Type/ValueMap pairs in the
1099 type planes. </dd>
1100
1101 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1102 <dd>Get a const_iterator that starts at the beginning of the type
1103 planes. The iterator will iterate over the Type/ValueMap pairs
1104 in the type planes. </dd>
1105
1106 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1107 <dd>Get an iterator at the end of the type planes. This serves as
1108 the marker for end of iteration over the type planes.</dd>
1109
1110 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1111 <dd>Get a const_iterator at the end of the type planes. This serves as
1112 the marker for end of iteration over the type planes.</dd>
1113
1114 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
1115 <dd>Get an iterator that starts at the beginning of a type plane.
1116 The iterator will iterate over the name/value pairs in the type plane.
1117 Note: The type plane must already exist before using this.</dd>
1118
1119 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
1120 <dd>Get a const_iterator that starts at the beginning of a type plane.
1121 The iterator will iterate over the name/value pairs in the type plane.
1122 Note: The type plane must already exist before using this.</dd>
1123
1124 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
1125 <dd>Get an iterator to the end of a type plane. This serves as the marker
1126 for end of iteration of the type plane.
1127 Note: The type plane must already exist before using this.</dd>
1128
1129 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
1130 <dd>Get a const_iterator to the end of a type plane. This serves as the
1131 marker for end of iteration of the type plane.
1132 Note: the type plane must already exist before using this.</dd>
1133
1134 <dt><tt>type_iterator type_begin()</tt>:</dt>
1135 <dd>Get an iterator to the start of the name/Type map.</dd>
1136
1137 <dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
1138 <dd> Get a const_iterator to the start of the name/Type map.</dd>
1139
1140 <dt><tt>type_iterator type_end()</tt>:</dt>
1141 <dd>Get an iterator to the end of the name/Type map. This serves as the
1142 marker for end of iteration of the types.</dd>
1143
1144 <dt><tt>type_const_iterator type_end() const</tt>:</dt>
1145 <dd>Get a const-iterator to the end of the name/Type map. This serves
1146 as the marker for end of iteration of the types.</dd>
1147
1148 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
1149 <dd>This method returns a plane_const_iterator for iteration over
1150 the type planes starting at a specific plane, given by \p Ty.</dd>
1151
1152 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
1153 <dd>This method returns a plane_iterator for iteration over the
1154 type planes starting at a specific plane, given by \p Ty.</dd>
1155
1156</dl>
1157</div>
1158
1159
1160
1161<!-- *********************************************************************** -->
1162<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1163 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
1164</div>
1165<!-- *********************************************************************** -->
1166
1167<div class="doc_text">
1168
1169<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1170being inspected or transformed. The core LLVM classes are defined in
1171header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1172the <tt>lib/VMCore</tt> directory.</p>
1173
1174</div>
1175
1176<!-- ======================================================================= -->
1177<div class="doc_subsection">
1178 <a name="Value">The <tt>Value</tt> class</a>
1179</div>
1180
1181<div>
1182
1183<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
1184<br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1185doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1186
1187<p>The <tt>Value</tt> class is the most important class in the LLVM Source
1188base. It represents a typed value that may be used (among other things) as an
1189operand to an instruction. There are many different types of <tt>Value</tt>s,
1190such as <a href="#Constant"><tt>Constant</tt></a>s,<a
1191href="#Argument"><tt>Argument</tt></a>s. Even <a
1192href="#Instruction"><tt>Instruction</tt></a>s and <a
1193href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
1194
1195<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
1196for a program. For example, an incoming argument to a function (represented
1197with an instance of the <a href="#Argument">Argument</a> class) is "used" by
1198every instruction in the function that references the argument. To keep track
1199of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
1200href="#User"><tt>User</tt></a>s that is using it (the <a
1201href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
1202graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
1203def-use information in the program, and is accessible through the <tt>use_</tt>*
1204methods, shown below.</p>
1205
1206<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
1207and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
1208method. In addition, all LLVM values can be named. The "name" of the
1209<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
1210
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1211 <pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1212
1213<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
1214that the name of any value may be missing (an empty string), so names should
1215<b>ONLY</b> be used for debugging (making the source code easier to read,
1216debugging printouts), they should not be used to keep track of values or map
1217between them. For this purpose, use a <tt>std::map</tt> of pointers to the
1218<tt>Value</tt> itself instead.</p>
1219
1220<p>One important aspect of LLVM is that there is no distinction between an SSA
1221variable and the operation that produces it. Because of this, any reference to
1222the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]1223argument, for example) is represented as a direct pointer to the instance of
1224the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1225represents this value. Although this may take some getting used to, it
1226simplifies the representation and makes it easier to manipulate.</p>
1227
1228</div>
1229
1230<!-- _______________________________________________________________________ -->
1231<div class="doc_subsubsection">
1232 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
1233</div>
1234
1235<div class="doc_text">
1236
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1237<ul>
1238 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
1239use-list<br>
1240 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
1241the use-list<br>
1242 <tt>unsigned use_size()</tt> - Returns the number of users of the
1243value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1244 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1245 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
1246the use-list.<br>
1247 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
1248use-list.<br>
1249 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
1250element in the list.
1251 <p> These methods are the interface to access the def-use
1252information in LLVM. As with all other iterators in LLVM, the naming
1253conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1254 </li>
1255 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1256 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1257 </li>
1258 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1259 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1260 <tt>void setName(const std::string &amp;Name)</tt>
1261 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
1262be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1263 </li>
1264 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1265
1266 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
1267 href="#User"><tt>User</tt>s</a> of the current value to refer to
1268 "<tt>V</tt>" instead. For example, if you detect that an instruction always
1269 produces a constant value (for example through constant folding), you can
1270 replace all uses of the instruction with the constant like this:</p>
1271
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1272 <pre> Inst-&gt;replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1273</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1274
1275</div>
1276
1277<!-- ======================================================================= -->
1278<div class="doc_subsection">
1279 <a name="User">The <tt>User</tt> class</a>
1280</div>
1281
1282<div class="doc_text">
1283
1284<p>
1285<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]1286doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1287Superclass: <a href="#Value"><tt>Value</tt></a></p>
1288
1289<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
1290refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1291that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1292referring to. The <tt>User</tt> class itself is a subclass of
1293<tt>Value</tt>.</p>
1294
1295<p>The operands of a <tt>User</tt> point directly to the LLVM <a
1296href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1297Single Assignment (SSA) form, there can only be one definition referred to,
1298allowing this direct connection. This connection provides the use-def
1299information in LLVM.</p>
1300
1301</div>
1302
1303<!-- _______________________________________________________________________ -->
1304<div class="doc_subsubsection">
1305 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
1306</div>
1307
1308<div class="doc_text">
1309
1310<p>The <tt>User</tt> class exposes the operand list in two ways: through
1311an index access interface and through an iterator based interface.</p>
1312
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1313<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1314 <li><tt>Value *getOperand(unsigned i)</tt><br>
1315 <tt>unsigned getNumOperands()</tt>
1316 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1317convenient form for direct access.</p></li>
1318
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1319 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
1320list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1321 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
1322the operand list.<br>
1323 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1324operand list.
1325 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1326the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1327</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1328
1329</div>
1330
1331<!-- ======================================================================= -->
1332<div class="doc_subsection">
1333 <a name="Instruction">The <tt>Instruction</tt> class</a>
1334</div>
1335
1336<div class="doc_text">
1337
1338<p><tt>#include "</tt><tt><a
1339href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1340doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1341Superclasses: <a href="#User"><tt>User</tt></a>, <a
1342href="#Value"><tt>Value</tt></a></p>
1343
1344<p>The <tt>Instruction</tt> class is the common base class for all LLVM
1345instructions. It provides only a few methods, but is a very commonly used
1346class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1347opcode (instruction type) and the parent <a
1348href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1349into. To represent a specific type of instruction, one of many subclasses of
1350<tt>Instruction</tt> are used.</p>
1351
1352<p> Because the <tt>Instruction</tt> class subclasses the <a
1353href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1354way as for other <a href="#User"><tt>User</tt></a>s (with the
1355<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1356<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
1357the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
1358file contains some meta-data about the various different types of instructions
1359in LLVM. It describes the enum values that are used as opcodes (for example
1360<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
1361concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
1362example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1363href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1364this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1365<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1366
1367</div>
1368
1369<!-- _______________________________________________________________________ -->
1370<div class="doc_subsubsection">
1371 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
1372 class</a>
1373</div>
1374
1375<div class="doc_text">
1376
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1377<ul>
1378 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1379 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
1380this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1381 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1382 <p>Returns true if the instruction writes to memory, i.e. it is a
1383 <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]1384 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1385 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1386 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1387 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1388in all ways to the original except that the instruction has no parent
1389(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1390and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1391</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1392
1393</div>
1394
1395<!-- ======================================================================= -->
1396<div class="doc_subsection">
1397 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1398</div>
1399
1400<div class="doc_text">
1401
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1402<p><tt>#include "<a
1403href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
1404doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
1405Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1406Superclass: <a href="#Value"><tt>Value</tt></a></p>
1407
1408<p>This class represents a single entry multiple exit section of the code,
1409commonly known as a basic block by the compiler community. The
1410<tt>BasicBlock</tt> class maintains a list of <a
1411href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
1412Matching the language definition, the last element of this list of instructions
1413is always a terminator instruction (a subclass of the <a
1414href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
1415
1416<p>In addition to tracking the list of instructions that make up the block, the
1417<tt>BasicBlock</tt> class also keeps track of the <a
1418href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
1419
1420<p>Note that <tt>BasicBlock</tt>s themselves are <a
1421href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1422like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1423<tt>label</tt>.</p>
1424
1425</div>
1426
1427<!-- _______________________________________________________________________ -->
1428<div class="doc_subsubsection">
1429 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
1430 class</a>
1431</div>
1432
1433<div class="doc_text">
1434
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1435<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1436
1437<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1438 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1439
1440<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1441insertion into a function. The constructor optionally takes a name for the new
1442block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
1443the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
1444automatically inserted at the end of the specified <a
1445href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1446manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
1447
1448<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1449<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1450<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1451<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]1452STL-style functions for accessing the instruction list.
1453
1454<p>These methods and typedefs are forwarding functions that have the same
1455semantics as the standard library methods of the same names. These methods
1456expose the underlying instruction list of a basic block in a way that is easy to
1457manipulate. To get the full complement of container operations (including
1458operations to update the list), you must use the <tt>getInstList()</tt>
1459method.</p></li>
1460
1461<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
1462
1463<p>This method is used to get access to the underlying container that actually
1464holds the Instructions. This method must be used when there isn't a forwarding
1465function in the <tt>BasicBlock</tt> class for the operation that you would like
1466to perform. Because there are no forwarding functions for "updating"
1467operations, you need to use this if you want to update the contents of a
1468<tt>BasicBlock</tt>.</p></li>
1469
1470<li><tt><a href="#Function">Function</a> *getParent()</tt>
1471
1472<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1473embedded into, or a null pointer if it is homeless.</p></li>
1474
1475<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
1476
1477<p> Returns a pointer to the terminator instruction that appears at the end of
1478the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1479instruction in the block is not a terminator, then a null pointer is
1480returned.</p></li>
1481
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1482</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1483
1484</div>
1485
1486<!-- ======================================================================= -->
1487<div class="doc_subsection">
1488 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1489</div>
1490
1491<div class="doc_text">
1492
1493<p><tt>#include "<a
1494href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1495doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
1496Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1497Superclasses: <a href="#User"><tt>User</tt></a>, <a
1498href="#Value"><tt>Value</tt></a></p>
1499
1500<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1501href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1502visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1503Because they are visible at global scope, they are also subject to linking with
1504other globals defined in different translation units. To control the linking
1505process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1506<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]1507defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1508
1509<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1510<tt>static</tt> in C), it is not visible to code outside the current translation
1511unit, and does not participate in linking. If it has external linkage, it is
1512visible to external code, and does participate in linking. In addition to
1513linkage information, <tt>GlobalValue</tt>s keep track of which <a
1514href="#Module"><tt>Module</tt></a> they are currently part of.</p>
1515
1516<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
1517by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
1518global is always a pointer to its contents. It is important to remember this
1519when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
1520be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
1521subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
1522int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
1523the address of the first element of this array and the value of the
1524<tt>GlobalVariable</tt> are the same, they have different types. The
1525<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
1526is <tt>int.</tt> Because of this, accessing a global value requires you to
1527dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
1528can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
1529Language Reference Manual</a>.</p>
1530
1531</div>
1532
1533<!-- _______________________________________________________________________ -->
1534<div class="doc_subsubsection">
1535 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
1536 class</a>
1537</div>
1538
1539<div class="doc_text">
1540
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1541<ul>
1542 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1543 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1544 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
1545 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
1546 <p> </p>
1547 </li>
1548 <li><tt><a href="#Module">Module</a> *getParent()</tt>
1549 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1550GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1551</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1552
1553</div>
1554
1555<!-- ======================================================================= -->
1556<div class="doc_subsection">
1557 <a name="Function">The <tt>Function</tt> class</a>
1558</div>
1559
1560<div class="doc_text">
1561
1562<p><tt>#include "<a
1563href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1564info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
1565Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1566href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
1567
1568<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
1569actually one of the more complex classes in the LLVM heirarchy because it must
1570keep track of a large amount of data. The <tt>Function</tt> class keeps track
1571of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
1572href="#Argument"><tt>Argument</tt></a>s, and a <a
1573href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
1574
1575<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
1576commonly used part of <tt>Function</tt> objects. The list imposes an implicit
1577ordering of the blocks in the function, which indicate how the code will be
1578layed out by the backend. Additionally, the first <a
1579href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1580<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
1581block. There are no implicit exit nodes, and in fact there may be multiple exit
1582nodes from a single <tt>Function</tt>. If the <a
1583href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1584the <tt>Function</tt> is actually a function declaration: the actual body of the
1585function hasn't been linked in yet.</p>
1586
1587<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1588<tt>Function</tt> class also keeps track of the list of formal <a
1589href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1590container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1591nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1592the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
1593
1594<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
1595LLVM feature that is only used when you have to look up a value by name. Aside
1596from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
1597internally to make sure that there are not conflicts between the names of <a
1598href="#Instruction"><tt>Instruction</tt></a>s, <a
1599href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1600href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
1601
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]1602<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
1603and therefore also a <a href="#Constant">Constant</a>. The value of the function
1604is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1605</div>
1606
1607<!-- _______________________________________________________________________ -->
1608<div class="doc_subsubsection">
1609 <a name="m_Function">Important Public Members of the <tt>Function</tt>
1610 class</a>
1611</div>
1612
1613<div class="doc_text">
1614
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1615<ul>
1616 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]1617 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1618
1619 <p>Constructor used when you need to create new <tt>Function</tt>s to add
1620 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]1621 create and what type of linkage the function should have. The <a
1622 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1623 specifies the formal arguments and return value for the function. The same
1624 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
1625 create multiple functions. The <tt>Parent</tt> argument specifies the Module
1626 in which the function is defined. If this argument is provided, the function
1627 will automatically be inserted into that module's list of
1628 functions.</p></li>
1629
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1630 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1631
1632 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
1633 function is "external", it does not have a body, and thus must be resolved
1634 by linking with a function defined in a different translation unit.</p></li>
1635
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1636 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1637 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1638
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1639 <tt>begin()</tt>, <tt>end()</tt>
1640 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1641
1642 <p>These are forwarding methods that make it easy to access the contents of
1643 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1644 list.</p></li>
1645
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1646 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1647
1648 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
1649 is necessary to use when you need to update the list or perform a complex
1650 action that doesn't have a forwarding method.</p></li>
1651
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]1652 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1653iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]1654 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1655
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1656 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]1657 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1658
1659 <p>These are forwarding methods that make it easy to access the contents of
1660 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
1661 list.</p></li>
1662
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1663 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1664
1665 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1666 necessary to use when you need to update the list or perform a complex
1667 action that doesn't have a forwarding method.</p></li>
1668
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1669 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1670
1671 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1672 function. Because the entry block for the function is always the first
1673 block, this returns the first block of the <tt>Function</tt>.</p></li>
1674
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1675 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1676 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1677
1678 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
1679 <tt>Function</tt> and returns the return type of the function, or the <a
1680 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
1681 function.</p></li>
1682
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1683 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1684
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1685 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1686 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1687</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1688
1689</div>
1690
1691<!-- ======================================================================= -->
1692<div class="doc_subsection">
1693 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1694</div>
1695
1696<div class="doc_text">
1697
1698<p><tt>#include "<a
1699href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
1700<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]1701doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1702Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1703href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
1704
1705<p>Global variables are represented with the (suprise suprise)
1706<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
1707subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
1708always referenced by their address (global values must live in memory, so their
1709"name" refers to their address). See <a
1710href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
1711may have an initial value (which must be a <a
1712href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
1713may be marked as "constant" themselves (indicating that their contents never
1714change at runtime).</p>
1715
1716</div>
1717
1718<!-- _______________________________________________________________________ -->
1719<div class="doc_subsubsection">
1720 <a name="m_GlobalVariable">Important Public Members of the
1721 <tt>GlobalVariable</tt> class</a>
1722</div>
1723
1724<div class="doc_text">
1725
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1726<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1727 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
1728 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
1729 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
1730
1731 <p>Create a new global variable of the specified type. If
1732 <tt>isConstant</tt> is true then the global variable will be marked as
1733 unchanging for the program. The Linkage parameter specifies the type of
1734 linkage (internal, external, weak, linkonce, appending) for the variable. If
1735 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
1736 the resultant global variable will have internal linkage. AppendingLinkage
1737 concatenates together all instances (in different translation units) of the
1738 variable into a single variable but is only applicable to arrays. &nbsp;See
1739 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
1740 further details on linkage types. Optionally an initializer, a name, and the
1741 module to put the variable into may be specified for the global variable as
1742 well.</p></li>
1743
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1744 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1745
1746 <p>Returns true if this is a global variable that is known not to
1747 be modified at runtime.</p></li>
1748
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1749 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1750
1751 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
1752
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1753 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1754
1755 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
1756 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1757</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1758
1759</div>
1760
1761<!-- ======================================================================= -->
1762<div class="doc_subsection">
1763 <a name="Module">The <tt>Module</tt> class</a>
1764</div>
1765
1766<div class="doc_text">
1767
1768<p><tt>#include "<a
1769href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]1770<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1771
1772<p>The <tt>Module</tt> class represents the top level structure present in LLVM
1773programs. An LLVM module is effectively either a translation unit of the
1774original program or a combination of several translation units merged by the
1775linker. The <tt>Module</tt> class keeps track of a list of <a
1776href="#Function"><tt>Function</tt></a>s, a list of <a
1777href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1778href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1779helpful member functions that try to make common operations easy.</p>
1780
1781</div>
1782
1783<!-- _______________________________________________________________________ -->
1784<div class="doc_subsubsection">
1785 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
1786</div>
1787
1788<div class="doc_text">
1789
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1790<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1791 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1792</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1793
1794<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
1795provide a name for it (probably based on the name of the translation unit).</p>
1796
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1797<ul>
1798 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1799 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1800
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1801 <tt>begin()</tt>, <tt>end()</tt>
1802 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1803
1804 <p>These are forwarding methods that make it easy to access the contents of
1805 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1806 list.</p></li>
1807
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1808 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1809
1810 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1811 necessary to use when you need to update the list or perform a complex
1812 action that doesn't have a forwarding method.</p>
1813
1814 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1815</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1816
1817<hr>
1818
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1819<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]1820 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1821
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]1822 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1823
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]1824 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]1825 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1826
1827 <p> These are forwarding methods that make it easy to access the contents of
1828 a <tt>Module</tt> object's <a
1829 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
1830
1831 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
1832
1833 <p>Returns the list of <a
1834 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
1835 use when you need to update the list or perform a complex action that
1836 doesn't have a forwarding method.</p>
1837
1838 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1839</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1840
1841<hr>
1842
1843<ul>
1844 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
1845
1846 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
1847 for this <tt>Module</tt>.</p>
1848
1849 <p><!-- Convenience methods --></p></li>
1850</ul>
1851
1852<hr>
1853
1854<ul>
1855 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
1856 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
1857
1858 <p>Look up the specified function in the <tt>Module</tt> <a
1859 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
1860 <tt>null</tt>.</p></li>
1861
1862 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
1863 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
1864
1865 <p>Look up the specified function in the <tt>Module</tt> <a
1866 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
1867 external declaration for the function and return it.</p></li>
1868
1869 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
1870
1871 <p>If there is at least one entry in the <a
1872 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
1873 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
1874 string.</p></li>
1875
1876 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
1877 href="#Type">Type</a> *Ty)</tt>
1878
1879 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
1880 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
1881 name, true is returned and the <a
1882 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
1883</ul>
1884
1885</div>
1886
1887<!-- ======================================================================= -->
1888<div class="doc_subsection">
1889 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
1890</div>
1891
1892<div class="doc_text">
1893
1894<p>Constant represents a base class for different types of constants. It
1895is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
1896ConstantArray etc for representing the various types of Constants.</p>
1897
1898</div>
1899
1900<!-- _______________________________________________________________________ -->
1901<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1902 <a name="m_Constant">Important Public Methods</a>
1903</div>
1904<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1905</div>
1906
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1907<!-- _______________________________________________________________________ -->
1908<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1909<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1910<ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1911 <li>ConstantSInt : This subclass of Constant represents a signed integer
1912 constant.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1913 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1914 <li><tt>int64_t getValue() const</tt>: Returns the underlying value of
1915 this constant. </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1916 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1917 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1918 <li>ConstantUInt : This class represents an unsigned integer.
1919 <ul>
1920 <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
1921 this constant. </li>
1922 </ul>
1923 </li>
1924 <li>ConstantFP : This class represents a floating point constant.
1925 <ul>
1926 <li><tt>double getValue() const</tt>: Returns the underlying value of
1927 this constant. </li>
1928 </ul>
1929 </li>
1930 <li>ConstantBool : This represents a boolean constant.
1931 <ul>
1932 <li><tt>bool getValue() const</tt>: Returns the underlying value of this
1933 constant. </li>
1934 </ul>
1935 </li>
1936 <li>ConstantArray : This represents a constant array.
1937 <ul>
1938 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1939 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1940 </ul>
1941 </li>
1942 <li>ConstantStruct : This represents a constant struct.
1943 <ul>
1944 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1945 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]1946 </ul>
1947 </li>
1948 <li>GlobalValue : This represents either a global variable or a function. In
1949 either case, the value is a constant fixed address (after linking).
1950 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1951</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1952</div>
1953
1954<!-- ======================================================================= -->
1955<div class="doc_subsection">
1956 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
1957</div>
1958
1959<div class="doc_text">
1960
1961<p>Type as noted earlier is also a subclass of a Value class. Any primitive
1962type (like int, short etc) in LLVM is an instance of Type Class. All other
1963types are instances of subclasses of type like FunctionType, ArrayType
1964etc. DerivedType is the interface for all such dervied types including
1965FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
1966be recursive (StructType). There exists exactly one instance of any type
1967structure at a time. This allows using pointer equality of Type *s for comparing
1968types.</p>
1969
1970</div>
1971
1972<!-- _______________________________________________________________________ -->
1973<div class="doc_subsubsection">
1974 <a name="m_Value">Important Public Methods</a>
1975</div>
1976
1977<div class="doc_text">
1978
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1979<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1980
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1981 <li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
1982 is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
1983 not true for Float and Double. </li>
1984
1985 <li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
1986 unsigned. This is not quite the complement of isSigned... nonnumeric types
1987 return false as they do with isSigned. This returns true for UByteTy,
1988 UShortTy, UIntTy, and ULongTy. </li>
1989
Chris Lattner4573f1b2004-07-08 17:49:37 +0000[diff] [blame]1990 <li><tt>bool isInteger() const</tt>: Equivalent to isSigned() || isUnsigned().</li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1991
1992 <li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
1993 type, which is either Bool type or one of the Integer types.</li>
1994
1995 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
1996 floating point types.</li>
1997
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1998 <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
1999 this type can be converted to 'Ty' without any reinterpretation of bits. For
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2000 example, uint to int or one pointer type to another.</li>
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2001</ul>
2002</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2003
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2004<!-- _______________________________________________________________________ -->
2005<div class="doc_subsubsection">
2006 <a name="m_Value">Important Derived Types</a>
2007</div>
2008<div class="doc_text">
2009<ul>
2010 <li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2011 <ul>
Reid Spencerc7d1d822004-11-01 09:16:30 +0000[diff] [blame]2012 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2013 of the elements in the sequential type. </li>
2014 </ul>
2015 </li>
2016 <li>ArrayType : This is a subclass of SequentialType and defines interface for
2017 array types.
2018 <ul>
2019 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2020 elements in the array. </li>
2021 </ul>
2022 </li>
2023 <li>PointerType : Subclass of SequentialType for pointer types. </li>
2024 <li>StructType : subclass of DerivedTypes for struct types </li>
2025 <li>FunctionType : subclass of DerivedTypes for function types.
2026 <ul>
2027 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2028 function</li>
2029 <li><tt> const Type * getReturnType() const</tt>: Returns the
2030 return type of the function.</li>
2031 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2032 the type of the ith parameter.</li>
2033 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2034 number of formal parameters.</li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2035 </ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2036 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2037</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2038</div>
2039
2040<!-- ======================================================================= -->
2041<div class="doc_subsection">
2042 <a name="Argument">The <tt>Argument</tt> class</a>
2043</div>
2044
2045<div class="doc_text">
2046
2047<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2048arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2049arguments. An argument has a pointer to the parent Function.</p>
2050
2051</div>
2052
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2053<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2054<hr>
2055<address>
2056 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
2057 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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2059 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
2060
2061 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2062 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
2063 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
2064 Last modified: $Date$
2065</address>
2066
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2067</body>
2068</html>
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]2069<!-- vim: sw=2 noai
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