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2<html><head><title>LLVM Programmer's Manual</title></head>
3
4<body bgcolor=white>
5
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]6<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
7<tr><td>&nbsp; <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM Programmer's Manual</b></font></td>
8</tr></table>
9
10<ol>
11 <li><a href="#introduction">Introduction</a>
12 <li><a href="#general">General Information</a>
13 <ul>
14 <li><a href="#stl">The C++ Standard Template Library</a>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]15 <li><a href="#isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt> and
16 <tt>dyn_cast&lt;&gt;</tt> templates</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]17 </ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]18 <li><a href="#common">Helpful Hints for Common Operations</a>
19 <ul>
20 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
21 <ul>
22 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
23 in a <tt>Function</tt></a>
24 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
25 in a <tt>BasicBlock</tt></a>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]26 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
27 in a <tt>Function</tt></a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]28 <li><a href="#iterate_convert">Turning an iterator into a class
29 pointer</a>
Chris Lattnerf1ebdc32002-09-06 22:09:21 +0000[diff] [blame]30 <li><a href="#iterate_complex">Finding call sites: a more complex
31 example</a>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]32 <li><a href="#iterate_chains">Iterating over def-use &amp; use-def
33 chains</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]34 </ul>
35 <li><a href="#simplechanges">Making simple changes</a>
36 <ul>
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]37 <li><a href="#schanges_creating">Creating and inserting new
38 <tt>Instruction</tt>s</a>
39 <li><a href="#schanges_deleting">Deleting
40 <tt>Instruction</tt>s</a>
41 <li><a href="#schanges_replacing">Replacing an
42 <tt>Instruction</tt> with another <tt>Value</tt></a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]43 </ul>
44<!--
45 <li>Working with the Control Flow Graph
46 <ul>
47 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
48 <li>
49 <li>
50 </ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]51 <li>Useful LLVM APIs
52 <ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]53 <li>The general graph API
54 <li>The <tt>InstVisitor</tt> template
55 <li>The DEBUG() macro
56 <li>The <tt>Statistic</tt> template
57-->
58 </ul>
59<!--
60 <li>Useful related topics
61 <ul>
62 <li>The <tt>-time-passes</tt> option
63 <li>How to use the LLVM Makefile system
64 <li>How to write a regression test
65 <li>
66 </ul>
67-->
68 </ul>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]69 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]70 <ul>
71 <li><a href="#Value">The <tt>Value</tt> class</a>
72 <ul>
73 <li><a href="#User">The <tt>User</tt> class</a>
74 <ul>
75 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
76 <ul>
77 <li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]78 </ul>
79 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
80 <ul>
81 <li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a>
82 <li><a href="#Function">The <tt>Function</tt> class</a>
83 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a>
84 </ul>
85 <li><a href="#Module">The <tt>Module</tt> class</a>
86 <li><a href="#Constant">The <tt>Constant</tt> class</a>
87 <ul>
88 <li>
89 <li>
90 </ul>
91 </ul>
92 <li><a href="#Type">The <tt>Type</tt> class</a>
93 <li><a href="#Argument">The <tt>Argument</tt> class</a>
94 </ul>
95 <li>The <tt>SymbolTable</tt> class
96 <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
97 <ul>
98 <li>Creating, inserting, moving and deleting from LLVM lists
99 </ul>
100 <li>Important iterator invalidation semantics to be aware of
101 </ul>
102
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]103 <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
104 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>, and
Chris Lattnerf1ebdc32002-09-06 22:09:21 +0000[diff] [blame]105 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a></b><p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]106</ol>
107
108
109<!-- *********************************************************************** -->
110<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
111<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
112<a name="introduction">Introduction
113</b></font></td></tr></table><ul>
114<!-- *********************************************************************** -->
115
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]116This document is meant to highlight some of the important classes and interfaces
117available in the LLVM source-base. This manual is not intended to explain what
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]118LLVM is, how it works, and what LLVM code looks like. It assumes that you know
119the basics of LLVM and are interested in writing transformations or otherwise
120analyzing or manipulating the code.<p>
121
122This document should get you oriented so that you can find your way in the
123continuously growing source code that makes up the LLVM infrastructure. Note
124that this manual is not intended to serve as a replacement for reading the
125source code, so if you think there should be a method in one of these classes to
126do something, but it's not listed, check the source. Links to the <a
127href="/doxygen/">doxygen</a> sources are provided to make this as easy as
128possible.<p>
129
130The first section of this document describes general information that is useful
131to know when working in the LLVM infrastructure, and the second describes the
132Core LLVM classes. In the future this manual will be extended with information
133describing how to use extension libraries, such as dominator information, CFG
134traversal routines, and useful utilities like the <tt><a
135href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
136
137
138<!-- *********************************************************************** -->
139</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
140<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
141<a name="general">General Information
142</b></font></td></tr></table><ul>
143<!-- *********************************************************************** -->
144
145This section contains general information that is useful if you are working in
146the LLVM source-base, but that isn't specific to any particular API.<p>
147
148
149<!-- ======================================================================= -->
150</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
151<tr><td>&nbsp;</td><td width="100%">&nbsp;
152<font color="#EEEEFF" face="Georgia,Palatino"><b>
153<a name="stl">The C++ Standard Template Library</a>
154</b></font></td></tr></table><ul>
155
156LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
157more than you are used to, or have seen before. Because of this, you might want
158to do a little background reading in the techniques used and capabilities of the
159library. There are many good pages that discuss the STL, and several books on
160the subject that you can get, so it will not be discussed in this document.<p>
161
162Here are some useful links:<p>
163<ol>
164<li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
165Library reference</a> - an excellent reference for the STL and other parts of
166the standard C++ library.<br>
167
168<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
169Questions</a>
170
171<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
172Contains a useful <a
173href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
174STL</a>.
175
176<li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
177Page</a>
178
179</ol><p>
180
181You are also encouraged to take a look at the <a
182href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
183to write maintainable code more than where to put your curly braces.<p>
184
185
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]186<!-- ======================================================================= -->
187</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
188<tr><td>&nbsp;</td><td width="100%">&nbsp;
189<font color="#EEEEFF" face="Georgia,Palatino"><b>
190<a name="isa">The isa&lt;&gt;, cast&lt;&gt; and dyn_cast&lt;&gt; templates</a>
191</b></font></td></tr></table><ul>
192
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]193The LLVM source-base makes extensive use of a custom form of RTTI. These
194templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
195operator, but they don't have some drawbacks (primarily stemming from the fact
196that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that have a v-table).
197Because they are used so often, you must know what they do and how they work.
198All of these templates are defined in the <a
199href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a> file (note
200that you very rarely have to include this file directly).<p>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]201
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]202<dl>
203
204<dt><tt>isa&lt;&gt;</tt>:
205
206<dd>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
207"<tt>instanceof</tt>" operator. It returns true or false depending on whether a
208reference or pointer points to an instance of the specified class. This can be
209very useful for constraint checking of various sorts (example below).<p>
210
211
212<dt><tt>cast&lt;&gt;</tt>:
213
214<dd>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
215converts a pointer or reference from a base class to a derived cast, causing an
216assertion failure if it is not really an instance of the right type. This
217should be used in cases where you have some information that makes you believe
218that something is of the right type. An example of the <tt>isa&lt;&gt;</tt> and
219<tt>cast&lt;&gt;</tt> template is:<p>
220
221<pre>
222static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
223 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))
224 return true;
225
226 <i>// Otherwise, it must be an instruction...</i>
227 return !L->contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)->getParent());
228</pre><p>
229
230Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed by a
231<tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt> operator.<p>
232
233
234<dt><tt>dyn_cast&lt;&gt;</tt>:
235
236<dd>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation. It
237checks to see if the operand is of the specified type, and if so, returns a
238pointer to it (this operator does not work with references). If the operand is
239not of the correct type, a null pointer is returned. Thus, this works very much
240like the <tt>dynamic_cast</tt> operator in C++, and should be used in the same
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]241circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt> operator is used in an
242<tt>if</tt> statement or some other flow control statement like this:<p>
243
244<pre>
245 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
246 ...
247 }
248</pre><p>
249
250This form of the <tt>if</tt> statement effectively combines together a call to
251<tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one statement,
252which is very convenient.<p>
253
254Another common example is:<p>
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]255
256<pre>
257 <i>// Loop over all of the phi nodes in a basic block</i>
258 BasicBlock::iterator BBI = BB->begin();
259 for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast&lt;<a href="#PHINode">PHINode</a>&gt;(&amp;*BBI); ++BBI)
260 cerr &lt;&lt; *PN;
261</pre><p>
262
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]263Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
264<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused. In
265particular you should not use big chained <tt>if/then/else</tt> blocks to check
266for lots of different variants of classes. If you find yourself wanting to do
267this, it is much cleaner and more efficient to use the InstVisitor class to
268dispatch over the instruction type directly.<p>
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]269
270
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]271<dt><tt>cast_or_null&lt;&gt;</tt>:
272
273<dd>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
274<tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as an
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]275argument (which it then propagates). This can sometimes be useful, allowing you
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]276to combine several null checks into one.<p>
277
278
279<dt><tt>dyn_cast_or_null&lt;&gt;</tt>:
280
281<dd>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
282<tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer as
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]283an argument (which it then propagates). This can sometimes be useful, allowing
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]284you to combine several null checks into one.<p>
285
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]286</dl>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]287
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]288These five templates can be used with any classes, whether they have a v-table
289or not. To add support for these templates, you simply need to add
290<tt>classof</tt> static methods to the class you are interested casting to.
291Describing this is currently outside the scope of this document, but there are
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]292lots of examples in the LLVM source base.<p>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]293
294
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]295
Chris Lattnerb99344f2002-09-06 16:40:10 +0000[diff] [blame]296<!-- *********************************************************************** -->
297</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
298<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
299<a name="common">Helpful Hints for Common Operations
300</b></font></td></tr></table><ul>
301<!-- *********************************************************************** -->
302
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]303This section describes how to perform some very simple transformations of LLVM
304code. This is meant to give examples of common idioms used, showing the
305practical side of LLVM transformations.<p>
306
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]307Because this is a "how-to" section, you should also read about the main classes
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]308that you will be working with. The <a href="#coreclasses">Core LLVM Class
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]309Hierarchy Reference</a> contains details and descriptions of the main classes
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]310that you should know about.<p>
311
312<!-- NOTE: this section should be heavy on example code -->
313
314
315<!-- ======================================================================= -->
316</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
317<tr><td>&nbsp;</td><td width="100%">&nbsp;
318<font color="#EEEEFF" face="Georgia,Palatino"><b>
319<a name="inspection">Basic Inspection and Traversal Routines</a>
320</b></font></td></tr></table><ul>
321
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]322The LLVM compiler infrastructure have many different data structures that may be
323traversed. Following the example of the C++ standard template library, the
324techniques used to traverse these various data structures are all basically the
325same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
326method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
327function returns an iterator pointing to one past the last valid element of the
328sequence, and there is some <tt>XXXiterator</tt> data type that is common
329between the two operations.<p>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]330
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]331Because the pattern for iteration is common across many different aspects of the
332program representation, the standard template library algorithms may be used on
333them, and it is easier to remember how to iterate. First we show a few common
334examples of the data structures that need to be traversed. Other data
335structures are traversed in very similar ways.<p>
336
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]337
338<!-- _______________________________________________________________________ -->
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]339</ul><h4><a name="iterate_function"><hr size=0>Iterating over the <a
340href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
341href="#Function"><tt>Function</tt></a> </h4><ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]342
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]343It's quite common to have a <tt>Function</tt> instance that you'd like
344to transform in some way; in particular, you'd like to manipulate its
345<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over
346all of the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>.
347The following is an example that prints the name of a
348<tt>BasicBlock</tt> and the number of <tt>Instruction</tt>s it
349contains:
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]350
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]351<pre>
352 // func is a pointer to a Function instance
353 for(Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {
354
355 // print out the name of the basic block if it has one, and then the
356 // number of instructions that it contains
357
Joel Stanley72ef35e2002-09-06 23:05:12 +0000[diff] [blame]358 cerr &lt;&lt "Basic block (name=" &lt;&lt i-&gt;getName() &lt;&lt; ") has "
359 &lt;&lt i-&gt;size() &lt;&lt " instructions.\n";
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]360 }
361</pre>
362
363Note that i can be used as if it were a pointer for the purposes of
364invoking member functions of the <tt>Instruction</tt> class. This is
365because the indirection operator is overloaded for the iterator
366classes. In the above code, the expression <tt>i->size()</tt> is
367exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]368
369<!-- _______________________________________________________________________ -->
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]370</ul><h4><a name="iterate_basicblock"><hr size=0>Iterating over the <a
371href="#Instruction"><tt>Instruction</tt></a>s in a <a
372href="#BasicBlock"><tt>BasicBlock</tt></a> </h4><ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]373
Joel Stanleyaaeb1c12002-09-06 23:42:40 +0000[diff] [blame]374Just like when dealing with <tt>BasicBlock</tt>s in
375<tt>Function</tt>s, it's easy to iterate over the individual
376instructions that make up <tt>BasicBlock</tt>s. Here's a code snippet
377that prints out each instruction in a <tt>BasicBlock</tt>:
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]378
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]379<pre>
380 // blk is a pointer to a BasicBlock instance
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]381 for(BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Chris Lattner2b763062002-09-06 22:51:10 +0000[diff] [blame]382 // the next statement works since operator&lt;&lt;(ostream&amp;,...)
383 // is overloaded for Instruction&amp;
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]384 cerr &lt;&lt; *i &lt;&lt; "\n";
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]385</pre>
386
387However, this isn't really the best way to print out the contents of a
388<tt>BasicBlock</tt>! Since the ostream operators are overloaded for
389virtually anything you'll care about, you could have just invoked the
Chris Lattner2b763062002-09-06 22:51:10 +0000[diff] [blame]390print routine on the basic block itself: <tt>cerr &lt;&lt; *blk &lt;&lt;
391"\n";</tt>.<p>
392
393Note that currently operator&lt;&lt; is implemented for <tt>Value*</tt>, so it
394will print out the contents of the pointer, instead of
395the pointer value you might expect. This is a deprecated interface that will
396be removed in the future, so it's best not to depend on it. To print out the
397pointer value for now, you must cast to <tt>void*</tt>.<p>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]398
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]399
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]400<!-- _______________________________________________________________________ -->
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]401</ul><h4><a name="iterate_institer"><hr size=0>Iterating over the <a
402href="#Instruction"><tt>Instruction</tt></a>s in a <a
403href="#Function"><tt>Function</tt></a></h4><ul>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]404
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]405If you're finding that you commonly iterate over a <tt>Function</tt>'s
406<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s
407<tt>Instruction</tt>s, <tt>InstIterator</tt> should be used instead.
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]408You'll need to include <a href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>, and then
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]409instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
410small example that shows how to dump all instructions in a function to
411stderr (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
412<tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&amp</tt>!):
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]413
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]414<pre>
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]415#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]416...
417// Suppose F is a ptr to a function
418for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
419 cerr &lt;&lt **i &lt;&lt "\n";
420</pre>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]421
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]422Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
423worklist with its initial contents. For example, if you wanted to
424initialize a worklist to contain all instructions in a
425<tt>Function</tt> F, all you would need to do is something like:
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]426
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]427<pre>
428std::set&lt;Instruction*&gt worklist;
429worklist.insert(inst_begin(F), inst_end(F));
430</pre>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]431
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]432The STL set <tt>worklist</tt> would now contain all instructions in
433the <tt>Function</tt> pointed to by F.
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]434
435<!-- _______________________________________________________________________ -->
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]436</ul><h4><a name="iterate_convert"><hr size=0>Turning an iterator into a class
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]437pointer (and vice-versa) </h4><ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]438
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]439Sometimes, it'll be useful to grab a reference (or pointer) to a class
440instance when all you've got at hand is an iterator. Well, extracting
441a reference or a pointer from an iterator is very straightforward.
442Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and
443<tt>j</tt> is a <tt>BasicBlock::const_iterator</tt>:
444
445<pre>
Chris Lattner83b5ee02002-09-06 22:12:58 +0000[diff] [blame]446 Instruction&amp; inst = *i; // grab reference to instruction reference
447 Instruction* pinst = &amp;*i; // grab pointer to instruction reference
448 const Instruction&amp; inst = *j;
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]449</pre>
450However, the iterators you'll be working with in the LLVM framework
451are special: they will automatically convert to a ptr-to-instance type
452whenever they need to. Instead of dereferencing the iterator and then
453taking the address of the result, you can simply assign the iterator
454to the proper pointer type and you get the dereference and address-of
455operation as a result of the assignment (behind the scenes, this is a
456result of overloading casting mechanisms). Thus the last line of the
457last example,
458
Chris Lattner83b5ee02002-09-06 22:12:58 +0000[diff] [blame]459<pre>Instruction* pinst = &amp;*i;</pre>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]460
461is semantically equivalent to
462
463<pre>Instruction* pinst = i;</pre>
464
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]465<b>Caveat emptor</b>: The above syntax works <i>only</i> when you're <i>not</i>
466working with <tt>dyn_cast</tt>. The template definition of <tt><a
467href="#isa">dyn_cast</a></tt> isn't implemented to handle this yet, so you'll
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]468still need the following in order for things to work properly:
469
470<pre>
471BasicBlock::iterator bbi = ...;
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]472<a href="#BranchInst">BranchInst</a>* b = <a href="#isa">dyn_cast</a>&lt;<a href="#BranchInst">BranchInst</a>&gt;(&amp;*bbi);
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]473</pre>
474
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]475It's also possible to turn a class pointer into the corresponding
476iterator. Usually, this conversion is quite inexpensive. The
477following code snippet illustrates use of the conversion constructors
478provided by LLVM iterators. By using these, you can explicitly grab
479the iterator of something without actually obtaining it via iteration
480over some structure:
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]481
482<pre>
483void printNextInstruction(Instruction* inst) {
484 BasicBlock::iterator it(inst);
485 ++it; // after this line, it refers to the instruction after *inst.
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]486 if(it != inst-&gt;getParent()->end()) cerr &lt;&lt; *it &lt;&lt; "\n";
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]487}
488</pre>
Joel Stanleyaaeb1c12002-09-06 23:42:40 +0000[diff] [blame]489Of course, this example is strictly pedagogical, because it'd be much
490better to explicitly grab the next instruction directly from inst.
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]491
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]492
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]493<!--_______________________________________________________________________-->
494</ul><h4><a name="iterate_complex"><hr size=0>Finding call sites: a slightly
495more complex example </h4><ul>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]496
497Say that you're writing a FunctionPass and would like to count all the
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]498locations in the entire module (that is, across every
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]499<tt>Function</tt>) where a certain function (i.e. some
500<tt>Function</tt>*) already in scope. As you'll learn later, you may
501want to use an <tt>InstVisitor</tt> to accomplish this in a much more
502straightforward manner, but this example will allow us to explore how
503you'd do it if you didn't have <tt>InstVisitor</tt> around. In
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]504pseudocode, this is what we want to do:
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]505
506<pre>
507initialize callCounter to zero
508for each Function f in the Module
509 for each BasicBlock b in f
510 for each Instruction i in b
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]511 if(i is a CallInst and calls the given function)
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]512 increment callCounter
513</pre>
514
515And the actual code is (remember, since we're writing a
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]516<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]517has to override the <tt>runOnFunction</tt> method...):
518
519<pre>
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]520Function* targetFunc = ...;
521
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]522class OurFunctionPass : public FunctionPass {
523 public:
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]524 OurFunctionPass(): callCounter(0) { }
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]525
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]526 virtual runOnFunction(Function&amp; F) {
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]527 for(Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
528 for(BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
Chris Lattnera9030cb2002-09-16 22:08:07 +0000[diff] [blame]529 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]530 // we know we've encountered a call instruction, so we
531 // need to determine if it's a call to the
532 // function pointed to by m_func or not.
533
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]534 if(callInst-&gt;getCalledFunction() == targetFunc)
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]535 ++callCounter;
536 }
537 }
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]538 }
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]539
540 private:
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]541 unsigned callCounter;
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]542};
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]543</pre>
544
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]545<!--_______________________________________________________________________-->
546</ul><h4><a name="iterate_chains"><hr size=0>Iterating over def-use &amp;
547use-def chains</h4><ul>
548
Joel Stanley01040b22002-09-11 20:50:04 +0000[diff] [blame]549Frequently, we might have an instance of the <a
550href="/doxygen/classValue.html">Value Class</a> and we want to
551determine which <tt>User</tt>s use the <tt>Value</tt>. The list of
552all <tt>User</tt>s of a particular <tt>Value</tt> is called a
553<i>def-use</i> chain. For example, let's say we have a
554<tt>Function*</tt> named <tt>F</tt> to a particular function
555<tt>foo</tt>. Finding all of the instructions that <i>use</i>
556<tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain of
557<tt>F</tt>:
558
559<pre>
560Function* F = ...;
561
562for(Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i) {
Chris Lattner24b70922002-09-17 22:43:00 +0000[diff] [blame]563 if(Instruction* Inst = dyn_cast&lt;Instruction&gt;(*i)) {
564 cerr &lt;&lt; "F is used in instruction:\n";
565 cerr &lt;&lt; *Inst &lt;&lt; "\n";
Joel Stanley01040b22002-09-11 20:50:04 +0000[diff] [blame]566 }
567}
568</pre>
569
570Alternately, it's common to have an instance of the <a
571href="/doxygen/classUser.html">User Class</a> and need to know what
572<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used
573by a <tt>User</tt> is known as a <i>use-def</i> chain. Instances of
574class <tt>Instruction</tt> are common <tt>User</tt>s, so we might want
575to iterate over all of the values that a particular instruction uses
576(that is, the operands of the particular <tt>Instruction</tt>):
577
578<pre>
579Instruction* pi = ...;
580
581for(User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]582 Value* v = *i;
Joel Stanley01040b22002-09-11 20:50:04 +0000[diff] [blame]583 ...
584}
585</pre>
586
587
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]588<!--
589 def-use chains ("finding all users of"): Value::use_begin/use_end
590 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
591-->
592
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]593<!-- ======================================================================= -->
594</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
595<tr><td>&nbsp;</td><td width="100%">&nbsp;
596<font color="#EEEEFF" face="Georgia,Palatino"><b>
597<a name="simplechanges">Making simple changes</a>
598</b></font></td></tr></table><ul>
599
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]600There are some primitive transformation operations present in the LLVM
601infrastructure that are worth knowing about. When performing
602transformations, it's fairly common to manipulate the contents of
603basic blocks. This section describes some of the common methods for
604doing so and gives example code.
605
606<!--_______________________________________________________________________-->
607</ul><h4><a name="schanges_creating"><hr size=0>Creating and inserting
608 new <tt>Instruction</tt>s</h4><ul>
609
610<i>Instantiating Instructions</i>
611
612<p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
613constructor for the kind of instruction to instantiate and provide the
614necessary parameters. For example, an <tt>AllocaInst</tt> only
615<i>requires</i> a (const-ptr-to) <tt>Type</tt>. Thus:
616
617<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
618
619will create an <tt>AllocaInst</tt> instance that represents the
620allocation of one integer in the current stack frame, at runtime.
621Each <tt>Instruction</tt> subclass is likely to have varying default
622parameters which change the semantics of the instruction, so refer to
Chris Lattner4e1f96b2002-09-12 19:06:51 +0000[diff] [blame]623the <a href="/doxygen/classInstruction.html">doxygen documentation for
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]624the subclass of Instruction</a> that you're interested in
625instantiating.</p>
626
627<p><i>Naming values</i></p>
628
629<p>
630It is very useful to name the values of instructions when you're able
631to, as this facilitates the debugging of your transformations. If you
632end up looking at generated LLVM machine code, you definitely want to
633have logical names associated with the results of instructions! By
634supplying a value for the <tt>Name</tt> (default) parameter of the
635<tt>Instruction</tt> constructor, you associate a logical name with
636the result of the instruction's execution at runtime. For example,
637say that I'm writing a transformation that dynamically allocates space
638for an integer on the stack, and that integer is going to be used as
639some kind of index by some other code. To accomplish this, I place an
640<tt>AllocaInst</tt> at the first point in the first
641<tt>BasicBlock</tt> of some <tt>Function</tt>, and I'm intending to
642use it within the same <tt>Function</tt>. I might do:
643
644<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
645
646where <tt>indexLoc</tt> is now the logical name of the instruction's
647execution value, which is a pointer to an integer on the runtime
648stack.
649</p>
650
651<p><i>Inserting instructions</i></p>
652
653<p>
654There are essentially two ways to insert an <tt>Instruction</tt> into
655an existing sequence of instructions that form a <tt>BasicBlock</tt>:
656<ul>
657<li>Insertion into an explicit instruction list
658
659<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within
660that <tt>BasicBlock</tt>, and a newly-created instruction
661we wish to insert before <tt>*pi</tt>, we do the following:
662
663<pre>
664BasicBlock* pb = ...;
665Instruction* pi = ...;
666Instruction* newInst = new Instruction(...);
667pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb
668</pre>
669</p>
670
671<li>Insertion into an implicit instruction list
672<p>
673<tt>Instruction</tt> instances that are already in
674<tt>BasicBlock</tt>s are implicitly associated with an existing
675instruction list: the instruction list of the enclosing basic block.
676Thus, we could have accomplished the same thing as the above code
677without being given a <tt>BasicBlock</tt> by doing:
678<pre>
679Instruction* pi = ...;
680Instruction* newInst = new Instruction(...);
681pi->getParent()->getInstList().insert(pi, newInst);
682</pre>
683In fact, this sequence of steps occurs so frequently that the
684<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes
685provide constructors which take (as a default parameter) a pointer to
686an <tt>Instruction</tt> which the newly-created <tt>Instruction</tt>
687should precede. That is, <tt>Instruction</tt> constructors are
688capable of inserting the newly-created instance into the
689<tt>BasicBlock</tt> of a provided instruction, immediately before that
690instruction. Using an <tt>Instruction</tt> constructor with a
691<tt>insertBefore</tt> (default) parameter, the above code becomes:
692<pre>
693Instruction* pi = ...;
694Instruction* newInst = new Instruction(..., pi);
695</pre>
696which is much cleaner, especially if you're creating a lot of
697instructions and adding them to <tt>BasicBlock</tt>s.
698</p>
699</p>
Chris Lattner9ebf5162002-09-12 19:08:16 +0000[diff] [blame]700</ul>
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]701
702<!--_______________________________________________________________________-->
703</ul><h4><a name="schanges_deleting"><hr size=0>Deleting
Chris Lattner4e1f96b2002-09-12 19:06:51 +0000[diff] [blame]704<tt>Instruction</tt>s</h4><ul>
705
706Deleting an instruction from an existing sequence of instructions that form a <a
707href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First, you
708must have a pointer to the instruction that you wish to delete. Second, you
709need to obtain the pointer to that instruction's basic block. You use the
710pointer to the basic block to get its list of instructions and then use the
711erase function to remove your instruction.<p>
712
713For example:<p>
714
715<pre>
716 <a href="#Instruction">Instruction</a> *I = .. ;
717 <a href="#BasicBlock">BasicBlock</a> *BB = I->getParent();
718 BB->getInstList().erase(I);
719</pre><p>
720
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]721
722<!--_______________________________________________________________________-->
723</ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
724 <tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
725
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]726<!-- Value::replaceAllUsesWith
727 User::replaceUsesOfWith
728 Point out: include/llvm/Transforms/Utils/
729 especially BasicBlockUtils.h with:
730 ReplaceInstWithValue, ReplaceInstWithInst
731
732-->
Chris Lattnerb99344f2002-09-06 16:40:10 +0000[diff] [blame]733
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]734<!-- *********************************************************************** -->
735</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
736<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]737<a name="coreclasses">The Core LLVM Class Hierarchy Reference
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]738</b></font></td></tr></table><ul>
739<!-- *********************************************************************** -->
740
741The Core LLVM classes are the primary means of representing the program being
742inspected or transformed. The core LLVM classes are defined in header files in
743the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
744directory.<p>
745
746
747<!-- ======================================================================= -->
748</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
749<tr><td>&nbsp;</td><td width="100%">&nbsp;
750<font color="#EEEEFF" face="Georgia,Palatino"><b>
751<a name="Value">The <tt>Value</tt> class</a>
752</b></font></td></tr></table><ul>
753
754<tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
755doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
756
757
758The <tt>Value</tt> class is the most important class in LLVM Source base. It
759represents a typed value that may be used (among other things) as an operand to
760an instruction. There are many different types of <tt>Value</tt>s, such as <a
761href="#Constant"><tt>Constant</tt></a>s, <a
762href="#Argument"><tt>Argument</tt></a>s, and even <a
763href="#Instruction"><tt>Instruction</tt></a>s and <a
764href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
765
766A particular <tt>Value</tt> may be used many times in the LLVM representation
767for a program. For example, an incoming argument to a function (represented
768with an instance of the <a href="#Argument">Argument</a> class) is "used" by
769every instruction in the function that references the argument. To keep track
770of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
771href="#User"><tt>User</tt></a>s that is using it (the <a
772href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
773graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]774def-use information in the program, and is accessible through the <tt>use_</tt>*
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]775methods, shown below.<p>
776
777Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
778this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
779method. <a name="#nameWarning">In addition, all LLVM values can be named. The
780"name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
781
782<pre>
783 %<b>foo</b> = add int 1, 2
784</pre>
785
786The name of this instruction is "foo". <b>NOTE</b> that the name of any value
787may be missing (an empty string), so names should <b>ONLY</b> be used for
788debugging (making the source code easier to read, debugging printouts), they
789should not be used to keep track of values or map between them. For this
790purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
791instead.<p>
792
793One important aspect of LLVM is that there is no distinction between an SSA
794variable and the operation that produces it. Because of this, any reference to
795the value produced by an instruction (or the value available as an incoming
796argument, for example) is represented as a direct pointer to the class that
797represents this value. Although this may take some getting used to, it
798simplifies the representation and makes it easier to manipulate.<p>
799
800
801<!-- _______________________________________________________________________ -->
802</ul><h4><a name="m_Value"><hr size=0>Important Public Members of
803the <tt>Value</tt> class</h4><ul>
804
805<li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
806 <tt>Value::use_const_iterator</tt>
807 - Typedef for const_iterator over the use-list<br>
808 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
809 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
810 <tt>use_iterator use_begin()</tt>
811 - Get an iterator to the start of the use-list.<br>
812 <tt>use_iterator use_end()</tt>
813 - Get an iterator to the end of the use-list.<br>
814 <tt><a href="#User">User</a> *use_back()</tt>
815 - Returns the last element in the list.<p>
816
817These methods are the interface to access the def-use information in LLVM. As with all other iterators in LLVM, the naming conventions follow the conventions defined by the <a href="#stl">STL</a>.<p>
818
819<li><tt><a href="#Type">Type</a> *getType() const</tt><p>
820This method returns the Type of the Value.
821
822<li><tt>bool hasName() const</tt><br>
823 <tt>std::string getName() const</tt><br>
824 <tt>void setName(const std::string &amp;Name)</tt><p>
825
826This family of methods is used to access and assign a name to a <tt>Value</tt>,
827be aware of the <a href="#nameWarning">precaution above</a>.<p>
828
829
830<li><tt>void replaceAllUsesWith(Value *V)</tt><p>
831
832This method traverses the use list of a <tt>Value</tt> changing all <a
Misha Brukmanc4f5bb02002-09-18 02:21:57 +0000[diff] [blame^]833href="#User"><tt>User</tt>s</a> of the current value to refer to "<tt>V</tt>"
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]834instead. For example, if you detect that an instruction always produces a
835constant value (for example through constant folding), you can replace all uses
836of the instruction with the constant like this:<p>
837
838<pre>
839 Inst-&gt;replaceAllUsesWith(ConstVal);
840</pre><p>
841
842
843
844<!-- ======================================================================= -->
845</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
846<tr><td>&nbsp;</td><td width="100%">&nbsp;
847<font color="#EEEEFF" face="Georgia,Palatino"><b>
848<a name="User">The <tt>User</tt> class</a>
849</b></font></td></tr></table><ul>
850
851<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
852doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
853Superclass: <a href="#Value"><tt>Value</tt></a><p>
854
855
856The <tt>User</tt> class is the common base class of all LLVM nodes that may
857refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
858that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
859referring to. The <tt>User</tt> class itself is a subclass of
860<tt>Value</tt>.<p>
861
862The operands of a <tt>User</tt> point directly to the LLVM <a
863href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
864Single Assignment (SSA) form, there can only be one definition referred to,
865allowing this direct connection. This connection provides the use-def
866information in LLVM.<p>
867
868<!-- _______________________________________________________________________ -->
869</ul><h4><a name="m_User"><hr size=0>Important Public Members of
870the <tt>User</tt> class</h4><ul>
871
872The <tt>User</tt> class exposes the operand list in two ways: through an index
873access interface and through an iterator based interface.<p>
874
875<li><tt>Value *getOperand(unsigned i)</tt><br>
876 <tt>unsigned getNumOperands()</tt><p>
877
878These two methods expose the operands of the <tt>User</tt> in a convenient form
879for direct access.<p>
880
881<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
882 <tt>User::op_const_iterator</tt>
883 <tt>use_iterator op_begin()</tt>
884 - Get an iterator to the start of the operand list.<br>
885 <tt>use_iterator op_end()</tt>
886 - Get an iterator to the end of the operand list.<p>
887
888Together, these methods make up the iterator based interface to the operands of
889a <tt>User</tt>.<p>
890
891
892
893<!-- ======================================================================= -->
894</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
895<tr><td>&nbsp;</td><td width="100%">&nbsp;
896<font color="#EEEEFF" face="Georgia,Palatino"><b>
897<a name="Instruction">The <tt>Instruction</tt> class</a>
898</b></font></td></tr></table><ul>
899
900<tt>#include "<a
901href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
902doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
903Superclasses: <a href="#User"><tt>User</tt></a>, <a
904href="#Value"><tt>Value</tt></a><p>
905
906The <tt>Instruction</tt> class is the common base class for all LLVM
907instructions. It provides only a few methods, but is a very commonly used
908class. The primary data tracked by the <tt>Instruction</tt> class itself is the
909opcode (instruction type) and the parent <a
910href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
911into. To represent a specific type of instruction, one of many subclasses of
912<tt>Instruction</tt> are used.<p>
913
914Because the <tt>Instruction</tt> class subclasses the <a
915href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
916way as for other <a href="#User"><tt>User</tt></a>s (with the
917<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
918<tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
919
Chris Lattner17635252002-09-12 17:18:46 +0000[diff] [blame]920An important file for the <tt>Instruction</tt> class is the
921<tt>llvm/Instruction.def</tt> file. This file contains some meta-data about the
922various different types of instructions in LLVM. It describes the enum values
923that are used as opcodes (for example <tt>Instruction::Add</tt> and
924<tt>Instruction::SetLE</tt>), as well as the concrete sub-classes of
925<tt>Instruction</tt> that implement the instruction (for example <tt><a
926href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
927href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
928this file confused doxygen, so these enum values don't show up correctly in the
929<a href="/doxygen/classInstruction.html">doxygen output</a>.<p>
930
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]931
932<!-- _______________________________________________________________________ -->
933</ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
934the <tt>Instruction</tt> class</h4><ul>
935
936<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
937
938Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
939<tt>Instruction</tt> is embedded into.<p>
940
941<li><tt>bool hasSideEffects()</tt><p>
942
943Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
944<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
945
946<li><tt>unsigned getOpcode()</tt><p>
947
948Returns the opcode for the <tt>Instruction</tt>.<p>
949
Chris Lattner17635252002-09-12 17:18:46 +0000[diff] [blame]950<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt><p>
951
952Returns another instance of the specified instruction, identical in all ways to
953the original except that the instruction has no parent (ie it's not embedded
954into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>), and it has no name.<p>
955
956
957
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]958<!--
959
960\subsection{Subclasses of Instruction :}
961\begin{itemize}
962<li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
963 \begin{itemize}
964 <li><tt>bool swapOperands()</tt>: Exchange the two operands to this instruction. If the instruction cannot be reversed (i.e. if it's a Div), it returns true.
965 \end{itemize}
966<li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
967 \begin{itemize}
968 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
969 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
970 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
971 \end{itemize}
972
973<li>PHINode : This represents the PHI instructions in the SSA form.
974 \begin{itemize}
975 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
976 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
977 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
978 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
979 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
980 Add an incoming value to the end of the PHI list
981 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
982 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
983 \end{itemize}
984<li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
985<li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
986 \begin{itemize}
987 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
988 \end{itemize}
989<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
990 \begin{itemize}
991 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
992 \end{itemize}
993<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
994 \begin{itemize}
995 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
996 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
997 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
998 \end{itemize}
999
1000\end{itemize}
1001
1002-->
1003
1004
1005<!-- ======================================================================= -->
1006</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1007<tr><td>&nbsp;</td><td width="100%">&nbsp;
1008<font color="#EEEEFF" face="Georgia,Palatino"><b>
1009<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1010</b></font></td></tr></table><ul>
1011
1012<tt>#include "<a
1013href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
1014doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
1015Superclass: <a href="#Value"><tt>Value</tt></a><p>
1016
1017
1018This class represents a single entry multiple exit section of the code, commonly
1019known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
1020maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
1021the body of the block. Matching the language definition, the last element of
1022this list of instructions is always a terminator instruction (a subclass of the
1023<a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
1024
1025In addition to tracking the list of instructions that make up the block, the
1026<tt>BasicBlock</tt> class also keeps track of the <a
1027href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
1028
1029Note that <tt>BasicBlock</tt>s themselves are <a
1030href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1031like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1032<tt>label</tt>.<p>
1033
1034
1035<!-- _______________________________________________________________________ -->
1036</ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
1037the <tt>BasicBlock</tt> class</h4><ul>
1038
1039<li><tt>BasicBlock(const std::string &amp;Name = "", <a
1040href="#Function">Function</a> *Parent = 0)</tt><p>
1041
1042The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1043insertion into a function. The constructor simply takes a name for the new
1044block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
1045into. If the <tt>Parent</tt> parameter is specified, the new
1046<tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
1047href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1048manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
1049
1050<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1051 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1052 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1053 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1054
1055These methods and typedefs are forwarding functions that have the same semantics
1056as the standard library methods of the same names. These methods expose the
1057underlying instruction list of a basic block in a way that is easy to
1058manipulate. To get the full complement of container operations (including
1059operations to update the list), you must use the <tt>getInstList()</tt>
1060method.<p>
1061
1062<li><tt>BasicBlock::InstListType &amp;getInstList()</tt><p>
1063
1064This method is used to get access to the underlying container that actually
1065holds the Instructions. This method must be used when there isn't a forwarding
1066function in the <tt>BasicBlock</tt> class for the operation that you would like
1067to perform. Because there are no forwarding functions for "updating"
1068operations, you need to use this if you want to update the contents of a
1069<tt>BasicBlock</tt>.<p>
1070
1071<li><tt><A href="#Function">Function</a> *getParent()</tt><p>
1072
1073Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1074embedded into, or a null pointer if it is homeless.<p>
1075
1076<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
1077
1078Returns a pointer to the terminator instruction that appears at the end of the
1079<tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1080instruction in the block is not a terminator, then a null pointer is
1081returned.<p>
1082
1083
1084<!-- ======================================================================= -->
1085</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1086<tr><td>&nbsp;</td><td width="100%">&nbsp;
1087<font color="#EEEEFF" face="Georgia,Palatino"><b>
1088<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1089</b></font></td></tr></table><ul>
1090
1091<tt>#include "<a
1092href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
1093doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
1094Superclasses: <a href="#User"><tt>User</tt></a>, <a
1095href="#Value"><tt>Value</tt></a><p>
1096
1097Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1098href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1099visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1100Because they are visible at global scope, they are also subject to linking with
1101other globals defined in different translation units. To control the linking
1102process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1103<tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
1104
1105If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1106<tt>static</tt> in C), it is not visible to code outside the current translation
1107unit, and does not participate in linking. If it has external linkage, it is
1108visible to external code, and does participate in linking. In addition to
1109linkage information, <tt>GlobalValue</tt>s keep track of which <a
1110href="#Module"><tt>Module</tt></a> they are currently part of.<p>
1111
1112Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
1113their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
1114always a pointer to its contents. This is explained in the LLVM Language
1115Reference Manual.<p>
1116
1117
1118<!-- _______________________________________________________________________ -->
1119</ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
1120the <tt>GlobalValue</tt> class</h4><ul>
1121
1122<li><tt>bool hasInternalLinkage() const</tt><br>
1123 <tt>bool hasExternalLinkage() const</tt><br>
1124 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
1125
1126These methods manipulate the linkage characteristics of the
1127<tt>GlobalValue</tt>.<p>
1128
1129<li><tt><a href="#Module">Module</a> *getParent()</tt><p>
1130
1131This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
1132currently embedded into.<p>
1133
1134
1135
1136<!-- ======================================================================= -->
1137</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1138<tr><td>&nbsp;</td><td width="100%">&nbsp;
1139<font color="#EEEEFF" face="Georgia,Palatino"><b>
1140<a name="Function">The <tt>Function</tt> class</a>
1141</b></font></td></tr></table><ul>
1142
1143<tt>#include "<a
1144href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
1145doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
1146Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1147href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1148
1149The <tt>Function</tt> class represents a single procedure in LLVM. It is
1150actually one of the more complex classes in the LLVM heirarchy because it must
1151keep track of a large amount of data. The <tt>Function</tt> class keeps track
1152of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
1153href="#Argument"><tt>Argument</tt></a>s, and a <a
1154href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
1155
1156The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
1157used part of <tt>Function</tt> objects. The list imposes an implicit ordering
1158of the blocks in the function, which indicate how the code will be layed out by
1159the backend. Additionally, the first <a
1160href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1161<tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
1162block. There are no implicit exit nodes, and in fact there may be multiple exit
1163nodes from a single <tt>Function</tt>. If the <a
1164href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1165the <tt>Function</tt> is actually a function declaration: the actual body of the
1166function hasn't been linked in yet.<p>
1167
1168In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1169<tt>Function</tt> class also keeps track of the list of formal <a
1170href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1171container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1172nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1173the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
1174
1175The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
1176feature that is only used when you have to look up a value by name. Aside from
1177that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
1178make sure that there are not conflicts between the names of <a
1179href="#Instruction"><tt>Instruction</tt></a>s, <a
1180href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1181href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
1182
1183
1184<!-- _______________________________________________________________________ -->
1185</ul><h4><a name="m_Function"><hr size=0>Important Public Members of
1186the <tt>Function</tt> class</h4><ul>
1187
1188<li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &amp;N = "")</tt><p>
1189
1190Constructor used when you need to create new <tt>Function</tt>s to add the the
1191program. The constructor must specify the type of the function to create and
1192whether or not it should start out with internal or external linkage.<p>
1193
1194<li><tt>bool isExternal()</tt><p>
1195
1196Return whether or not the <tt>Function</tt> has a body defined. If the function
1197is "external", it does not have a body, and thus must be resolved by linking
1198with a function defined in a different translation unit.<p>
1199
1200
1201<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
1202 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
1203 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1204 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1205
1206These are forwarding methods that make it easy to access the contents of a
1207<tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1208list.<p>
1209
1210<li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt><p>
1211
1212Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
1213neccesary to use when you need to update the list or perform a complex action
1214that doesn't have a forwarding method.<p>
1215
1216
1217<li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
1218 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
1219 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
1220 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
1221
1222These are forwarding methods that make it easy to access the contents of a
1223<tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
1224
1225<li><tt>Function::ArgumentListType &amp;getArgumentList()</tt><p>
1226
1227Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1228neccesary to use when you need to update the list or perform a complex action
1229that doesn't have a forwarding method.<p>
1230
1231
1232
1233<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
1234
1235Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1236function. Because the entry block for the function is always the first block,
1237this returns the first block of the <tt>Function</tt>.<p>
1238
1239<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1240 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
1241
1242This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
1243and returns the return type of the function, or the <a
1244href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
1245
1246
1247<li><tt>bool hasSymbolTable() const</tt><p>
1248
1249Return true if the <tt>Function</tt> has a symbol table allocated to it and if
1250there is at least one entry in it.<p>
1251
1252<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1253
1254Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1255<tt>Function</tt> or a null pointer if one has not been allocated (because there
1256are no named values in the function).<p>
1257
1258<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
1259
1260Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1261<tt>Function</tt> or allocate a new <a
1262href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
1263should only be used when adding elements to the <a
1264href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
1265not left laying around.<p>
1266
1267
1268
1269<!-- ======================================================================= -->
1270</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1271<tr><td>&nbsp;</td><td width="100%">&nbsp;
1272<font color="#EEEEFF" face="Georgia,Palatino"><b>
1273<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1274</b></font></td></tr></table><ul>
1275
1276<tt>#include "<a
1277href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
1278doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
1279Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1280href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1281
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1282Global variables are represented with the (suprise suprise)
1283<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
1284also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
1285are always referenced by their address (global values must live in memory, so
1286their "name" refers to their address). Global variables may have an initial
1287value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
1288have an initializer, they may be marked as "constant" themselves (indicating
1289that their contents never change at runtime).<p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1290
1291
1292<!-- _______________________________________________________________________ -->
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1293</ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
1294<tt>GlobalVariable</tt> class</h4><ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1295
1296<li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
1297isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
1298&amp;Name = "")</tt><p>
1299
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1300Create a new global variable of the specified type. If <tt>isConstant</tt> is
1301true then the global variable will be marked as unchanging for the program, and
1302if <tt>isInternal</tt> is true the resultant global variable will have internal
1303linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
1304
1305
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1306<li><tt>bool isConstant() const</tt><p>
1307
1308Returns true if this is a global variable is known not to be modified at
1309runtime.<p>
1310
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1311
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1312<li><tt>bool hasInitializer()</tt><p>
1313
1314Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
1315
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1316
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1317<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
1318
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1319Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
1320this method if there is no initializer.<p>
1321
1322
1323<!-- ======================================================================= -->
1324</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1325<tr><td>&nbsp;</td><td width="100%">&nbsp;
1326<font color="#EEEEFF" face="Georgia,Palatino"><b>
1327<a name="Module">The <tt>Module</tt> class</a>
1328</b></font></td></tr></table><ul>
1329
1330<tt>#include "<a
1331href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
1332doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
1333
1334The <tt>Module</tt> class represents the top level structure present in LLVM
1335programs. An LLVM module is effectively either a translation unit of the
1336original program or a combination of several translation units merged by the
1337linker. The <tt>Module</tt> class keeps track of a list of <a
1338href="#Function"><tt>Function</tt></a>s, a list of <a
1339href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1340href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1341helpful member functions that try to make common operations easy.<p>
1342
1343
1344<!-- _______________________________________________________________________ -->
1345</ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
1346<tt>Module</tt> class</h4><ul>
1347
1348<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
1349 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
1350 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1351 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1352
1353These are forwarding methods that make it easy to access the contents of a
1354<tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1355list.<p>
1356
1357<li><tt>Module::FunctionListType &amp;getFunctionList()</tt><p>
1358
1359Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1360neccesary to use when you need to update the list or perform a complex action
1361that doesn't have a forwarding method.<p>
1362
1363<!-- Global Variable -->
1364<hr size=0>
1365
1366<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
1367 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
1368 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
1369 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
1370
1371These are forwarding methods that make it easy to access the contents of a
1372<tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
1373list.<p>
1374
1375<li><tt>Module::GlobalListType &amp;getGlobalList()</tt><p>
1376
1377Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
1378This is neccesary to use when you need to update the list or perform a complex
1379action that doesn't have a forwarding method.<p>
1380
1381
1382<!-- Symbol table stuff -->
1383<hr size=0>
1384
1385<li><tt>bool hasSymbolTable() const</tt><p>
1386
1387Return true if the <tt>Module</tt> has a symbol table allocated to it and if
1388there is at least one entry in it.<p>
1389
1390<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1391
1392Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1393<tt>Module</tt> or a null pointer if one has not been allocated (because there
1394are no named values in the function).<p>
1395
1396<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
1397
1398Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1399<tt>Module</tt> or allocate a new <a
1400href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
1401should only be used when adding elements to the <a
1402href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
1403not left laying around.<p>
1404
1405
1406<!-- Convenience methods -->
1407<hr size=0>
1408
1409<li><tt><a href="#Function">Function</a> *getFunction(const std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
1410
1411Look up the specified function in the <tt>Module</tt> <a
1412href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
1413<tt>null</tt>.<p>
1414
1415
1416<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
1417 &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
1418
1419Look up the specified function in the <tt>Module</tt> <a
1420href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
1421external declaration for the function and return it.<p>
1422
1423
1424<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
1425
1426If there is at least one entry in the <a
1427href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
1428href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
1429string.<p>
1430
1431
1432<li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
1433*Ty)</tt><p>
1434
1435Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
1436<tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
1437is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
1438modified.<p>
1439
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1440
1441<!-- ======================================================================= -->
1442</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1443<tr><td>&nbsp;</td><td width="100%">&nbsp;
1444<font color="#EEEEFF" face="Georgia,Palatino"><b>
1445<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
1446</b></font></td></tr></table><ul>
1447
1448Constant represents a base class for different types of constants. It is
1449subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
1450ConstantArray etc for representing the various types of Constants.<p>
1451
1452
1453<!-- _______________________________________________________________________ -->
1454</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1455
1456<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
1457
1458
1459
1460
1461\subsection{Important Subclasses of Constant}
1462\begin{itemize}
1463<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
1464 \begin{itemize}
1465 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
1466 \end{itemize}
1467<li>ConstantUInt : This class represents an unsigned integer.
1468 \begin{itemize}
1469 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
1470 \end{itemize}
1471<li>ConstantFP : This class represents a floating point constant.
1472 \begin{itemize}
1473 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
1474 \end{itemize}
1475<li>ConstantBool : This represents a boolean constant.
1476 \begin{itemize}
1477 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
1478 \end{itemize}
1479<li>ConstantArray : This represents a constant array.
1480 \begin{itemize}
1481 <li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1482 \end{itemize}
1483<li>ConstantStruct : This represents a constant struct.
1484 \begin{itemize}
1485 <li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1486 \end{itemize}
1487<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
1488 \begin{itemize}
1489<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
1490 \end{itemize}
1491\end{itemize}
1492
1493
1494<!-- ======================================================================= -->
1495</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1496<tr><td>&nbsp;</td><td width="100%">&nbsp;
1497<font color="#EEEEFF" face="Georgia,Palatino"><b>
1498<a name="Type">The <tt>Type</tt> class and Derived Types</a>
1499</b></font></td></tr></table><ul>
1500
1501Type as noted earlier is also a subclass of a Value class. Any primitive
1502type (like int, short etc) in LLVM is an instance of Type Class. All
1503other types are instances of subclasses of type like FunctionType,
1504ArrayType etc. DerivedType is the interface for all such dervied types
1505including FunctionType, ArrayType, PointerType, StructType. Types can have
1506names. They can be recursive (StructType). There exists exactly one instance
1507of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
1508
1509<!-- _______________________________________________________________________ -->
1510</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1511
1512<li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
1513<li><tt> bool isSigned () const</tt>: Returns whether an integral numeric type is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is not true for Float and Double.
1514<li><tt>bool isUnsigned () const</tt>: Returns whether a numeric type is unsigned. This is not quite the complement of isSigned... nonnumeric types return false as they do with isSigned. This returns true for UByteTy, UShortTy, UIntTy, and ULongTy.
1515<li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
1516<li><tt>bool isIntegral () const</tt>: Returns true if this is an integral type, which is either Bool type or one of the Integer types.
1517
1518<li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
1519<li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
1520<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if this type can be converted to 'Ty' without any reinterpretation of bits. For example, uint to int.
1521<li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
1522<li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
1523<li><tt>const Type * getContainedType (unsigned i) const</tt>:
1524This method is used to implement the type iterator. For derived types, this returns the types 'contained' in the derived type, returning 0 when 'i' becomes invalid. This allows the user to iterate over the types in a struct, for example, really easily.
1525<li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
1526
1527
1528
1529\subsection{Derived Types}
1530\begin{itemize}
1531<li>SequentialType : This is subclassed by ArrayType and PointerType
1532 \begin{itemize}
1533 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
1534 \end{itemize}
1535<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
1536 \begin{itemize}
1537 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
1538 \end{itemize}
1539<li>PointerType : Subclass of SequentialType for pointer types.
1540<li>StructType : subclass of DerivedTypes for struct types
1541<li>FunctionType : subclass of DerivedTypes for function types.
1542 \begin{itemize}
1543
1544 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
1545 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
1546 <li><tt> const ParamTypes &amp;getParamTypes () const</tt>: Returns a vector of parameter types.
1547 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
1548 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
1549 \end{itemize}
1550\end{itemize}
1551
1552
1553
1554
1555<!-- ======================================================================= -->
1556</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1557<tr><td>&nbsp;</td><td width="100%">&nbsp;
1558<font color="#EEEEFF" face="Georgia,Palatino"><b>
1559<a name="Argument">The <tt>Argument</tt> class</a>
1560</b></font></td></tr></table><ul>
1561
1562This subclass of Value defines the interface for incoming formal arguments to a
1563function. A Function maitanis a list of its formal arguments. An argument has a
1564pointer to the parent Function.
1565
1566
1567
1568
1569<!-- *********************************************************************** -->
1570</ul>
1571<!-- *********************************************************************** -->
1572
1573<hr><font size-1>
1574<address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
1575<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
1576<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
1577<!-- hhmts start -->
Chris Lattner24b70922002-09-17 22:43:00 +0000[diff] [blame]1578Last modified: Tue Sep 17 17:41:54 CDT 2002
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1579<!-- hhmts end -->
1580</font></body></html>