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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 Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]15<!--
16 <li>The <tt>-time-passes</tt> option
17 <li>How to use the LLVM Makefile system
18 <li>How to write a regression test
19-->
20 </ul>
21 <li><a href="#apis">Important and useful LLVM APIs</a>
22 <ul>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]23 <li><a href="#isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt> and
24 <tt>dyn_cast&lt;&gt;</tt> templates</a>
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]25 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro &amp;
26 <tt>-debug</tt> option</a>
27 <li><a href="#Statistic">The <tt>Statistic</tt> template &amp;
28 <tt>-stats</tt> option</a>
29<!--
30 <li>The <tt>InstVisitor</tt> template
31 <li>The general graph API
32-->
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]33 </ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]34 <li><a href="#common">Helpful Hints for Common Operations</a>
35 <ul>
36 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
37 <ul>
38 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
39 in a <tt>Function</tt></a>
40 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
41 in a <tt>BasicBlock</tt></a>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]42 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
43 in a <tt>Function</tt></a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]44 <li><a href="#iterate_convert">Turning an iterator into a class
45 pointer</a>
Chris Lattnerf1ebdc32002-09-06 22:09:21 +0000[diff] [blame]46 <li><a href="#iterate_complex">Finding call sites: a more complex
47 example</a>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]48 <li><a href="#iterate_chains">Iterating over def-use &amp; use-def
49 chains</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]50 </ul>
51 <li><a href="#simplechanges">Making simple changes</a>
52 <ul>
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]53 <li><a href="#schanges_creating">Creating and inserting new
54 <tt>Instruction</tt>s</a>
55 <li><a href="#schanges_deleting">Deleting
56 <tt>Instruction</tt>s</a>
57 <li><a href="#schanges_replacing">Replacing an
58 <tt>Instruction</tt> with another <tt>Value</tt></a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]59 </ul>
60<!--
61 <li>Working with the Control Flow Graph
62 <ul>
63 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
64 <li>
65 <li>
66 </ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]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>
Chris Lattnerab0577b2002-09-22 21:25:12 +0000[diff] [blame]164<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]165Library reference</a> - an excellent reference for the STL and other parts of
Chris Lattnere9ddc7f2002-10-21 02:38:02 +0000[diff] [blame]166the standard C++ library.
167
168<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
169O'Reilly book in the making. It has a decent <a
170href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
171Reference</a> that rivals Dinkumware's, and is actually free until the book is
172published.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]173
174<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
175Questions</a>
176
177<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
178Contains a useful <a
179href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
180STL</a>.
181
182<li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
183Page</a>
184
185</ol><p>
186
187You are also encouraged to take a look at the <a
188href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
189to write maintainable code more than where to put your curly braces.<p>
190
191
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]192<!-- *********************************************************************** -->
193</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
194<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
195<a name="apis">Important and useful LLVM APIs
196</b></font></td></tr></table><ul>
197<!-- *********************************************************************** -->
198
199Here we highlight some LLVM APIs that are generally useful and good to know
200about when writing transformations.<p>
201
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]202<!-- ======================================================================= -->
203</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
204<tr><td>&nbsp;</td><td width="100%">&nbsp;
205<font color="#EEEEFF" face="Georgia,Palatino"><b>
206<a name="isa">The isa&lt;&gt;, cast&lt;&gt; and dyn_cast&lt;&gt; templates</a>
207</b></font></td></tr></table><ul>
208
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]209The LLVM source-base makes extensive use of a custom form of RTTI. These
210templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
211operator, but they don't have some drawbacks (primarily stemming from the fact
212that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that have a v-table).
213Because they are used so often, you must know what they do and how they work.
214All of these templates are defined in the <a
215href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a> file (note
216that you very rarely have to include this file directly).<p>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]217
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]218<dl>
219
220<dt><tt>isa&lt;&gt;</tt>:
221
222<dd>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
223"<tt>instanceof</tt>" operator. It returns true or false depending on whether a
224reference or pointer points to an instance of the specified class. This can be
225very useful for constraint checking of various sorts (example below).<p>
226
227
228<dt><tt>cast&lt;&gt;</tt>:
229
230<dd>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
231converts a pointer or reference from a base class to a derived cast, causing an
232assertion failure if it is not really an instance of the right type. This
233should be used in cases where you have some information that makes you believe
234that something is of the right type. An example of the <tt>isa&lt;&gt;</tt> and
235<tt>cast&lt;&gt;</tt> template is:<p>
236
237<pre>
238static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
239 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))
240 return true;
241
242 <i>// Otherwise, it must be an instruction...</i>
243 return !L->contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)->getParent());
244</pre><p>
245
246Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed by a
247<tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt> operator.<p>
248
249
250<dt><tt>dyn_cast&lt;&gt;</tt>:
251
252<dd>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation. It
253checks to see if the operand is of the specified type, and if so, returns a
254pointer to it (this operator does not work with references). If the operand is
255not of the correct type, a null pointer is returned. Thus, this works very much
256like 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]257circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt> operator is used in an
258<tt>if</tt> statement or some other flow control statement like this:<p>
259
260<pre>
261 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
262 ...
263 }
264</pre><p>
265
266This form of the <tt>if</tt> statement effectively combines together a call to
267<tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one statement,
268which is very convenient.<p>
269
270Another common example is:<p>
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]271
272<pre>
273 <i>// Loop over all of the phi nodes in a basic block</i>
274 BasicBlock::iterator BBI = BB->begin();
Chris Lattner6a547102003-04-23 16:26:15 +0000[diff] [blame]275 for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast&lt;<a href="#PHINode">PHINode</a>&gt;(BBI); ++BBI)
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]276 cerr &lt;&lt; *PN;
277</pre><p>
278
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]279Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
280<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused. In
281particular you should not use big chained <tt>if/then/else</tt> blocks to check
282for lots of different variants of classes. If you find yourself wanting to do
283this, it is much cleaner and more efficient to use the InstVisitor class to
284dispatch over the instruction type directly.<p>
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]285
286
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]287<dt><tt>cast_or_null&lt;&gt;</tt>:
288
289<dd>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
290<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]291argument (which it then propagates). This can sometimes be useful, allowing you
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]292to combine several null checks into one.<p>
293
294
295<dt><tt>dyn_cast_or_null&lt;&gt;</tt>:
296
297<dd>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
298<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]299an argument (which it then propagates). This can sometimes be useful, allowing
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]300you to combine several null checks into one.<p>
301
Chris Lattner979d9b72002-09-10 00:39:05 +0000[diff] [blame]302</dl>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]303
Chris Lattner6b121f12002-09-10 15:20:46 +0000[diff] [blame]304These five templates can be used with any classes, whether they have a v-table
305or not. To add support for these templates, you simply need to add
306<tt>classof</tt> static methods to the class you are interested casting to.
307Describing this is currently outside the scope of this document, but there are
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]308lots of examples in the LLVM source base.<p>
Chris Lattner1d43fd42002-09-09 05:53:21 +0000[diff] [blame]309
310
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]311<!-- ======================================================================= -->
312</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
313<tr><td>&nbsp;</td><td width="100%">&nbsp;
314<font color="#EEEEFF" face="Georgia,Palatino"><b>
315<a name="DEBUG">The <tt>DEBUG()</tt> macro &amp; <tt>-debug</tt> option</a>
316</b></font></td></tr></table><ul>
317
318Often when working on your pass you will put a bunch of debugging printouts and
319other code into your pass. After you get it working, you want to remove
320it... but you may need it again in the future (to work out new bugs that you run
321across).<p>
322
323Naturally, because of this, you don't want to delete the debug printouts, but
324you don't want them to always be noisy. A standard compromise is to comment
325them out, allowing you to enable them if you need them in the future.<p>
326
327The "<tt><a
Chris Lattner8328f1d2002-10-01 22:39:41 +0000[diff] [blame]328href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>"
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]329file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
330this problem. Basically, you can put arbitrary code into the argument of the
331<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' is run with the
332'<tt>-debug</tt>' command line argument:
333
334<pre>
335 ...
336 DEBUG(std::cerr &lt;&lt; "I am here!\n");
337 ...
338</pre><p>
339
340Then you can run your pass like this:<p>
341
342<pre>
343 $ opt &lt; a.bc &gt; /dev/null -mypass
344 &lt;no output&gt;
345 $ opt &lt; a.bc &gt; /dev/null -mypass -debug
346 I am here!
347 $
348</pre><p>
349
350Using the <tt>DEBUG()</tt> macro instead of a home brewed solution allows you to
351now have to create "yet another" command line option for the debug output for
Chris Lattnera4e7c4e2002-11-08 06:50:02 +0000[diff] [blame]352your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
353so they do not cause a performance impact at all (for the same reason, they
354should also not contain side-effects!).<p>
355
356One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
357enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
358"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
359program hasn't been started yet, you can always just run it with
360<tt>-debug</tt>.<p>
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]361
362
363<!-- ======================================================================= -->
364</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
365<tr><td>&nbsp;</td><td width="100%">&nbsp;
366<font color="#EEEEFF" face="Georgia,Palatino"><b>
367<a name="Statistic">The <tt>Statistic</tt> template &amp; <tt>-stats</tt>
368option</a>
369</b></font></td></tr></table><ul>
370
371The "<tt><a
Chris Lattner8328f1d2002-10-01 22:39:41 +0000[diff] [blame]372href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>"
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]373file provides a template named <tt>Statistic</tt> that is used as a unified way
374to keeping track of what the LLVM compiler is doing and how effective various
375optimizations are. It is useful to see what optimizations are contributing to
376making a particular program run faster.<p>
377
378Often you may run your pass on some big program, and you're interested to see
379how many times it makes a certain transformation. Although you can do this with
380hand inspection, or some ad-hoc method, this is a real pain and not very useful
381for big programs. Using the <tt>Statistic</tt> template makes it very easy to
382keep track of this information, and the calculated information is presented in a
383uniform manner with the rest of the passes being executed.<p>
384
385There are many examples of <tt>Statistic</tt> users, but this basics of using it
386are as follows:<p>
387
388<ol>
389<li>Define your statistic like this:<p>
390
391<pre>
Chris Lattner8328f1d2002-10-01 22:39:41 +0000[diff] [blame]392static Statistic&lt;&gt; NumXForms("mypassname", "The # of times I did stuff");
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]393</pre><p>
394
395The <tt>Statistic</tt> template can emulate just about any data-type, but if you
396do not specify a template argument, it defaults to acting like an unsigned int
397counter (this is usually what you want).<p>
398
399<li>Whenever you make a transformation, bump the counter:<p>
400
401<pre>
402 ++NumXForms; // I did stuff
403</pre><p>
404
405</ol><p>
406
407That's all you have to do. To get '<tt>opt</tt>' to print out the statistics
408gathered, use the '<tt>-stats</tt>' option:<p>
409
410<pre>
411 $ opt -stats -mypassname &lt; program.bc &gt; /dev/null
412 ... statistic output ...
413</pre><p>
414
415When running <tt>gccas</tt> on a C file from the SPEC benchmark suite, it gives
416a report that looks like this:<p>
417
418<pre>
419 7646 bytecodewriter - Number of normal instructions
420 725 bytecodewriter - Number of oversized instructions
421 129996 bytecodewriter - Number of bytecode bytes written
422 2817 raise - Number of insts DCEd or constprop'd
423 3213 raise - Number of cast-of-self removed
424 5046 raise - Number of expression trees converted
425 75 raise - Number of other getelementptr's formed
426 138 raise - Number of load/store peepholes
427 42 deadtypeelim - Number of unused typenames removed from symtab
428 392 funcresolve - Number of varargs functions resolved
429 27 globaldce - Number of global variables removed
430 2 adce - Number of basic blocks removed
431 134 cee - Number of branches revectored
432 49 cee - Number of setcc instruction eliminated
433 532 gcse - Number of loads removed
434 2919 gcse - Number of instructions removed
435 86 indvars - Number of cannonical indvars added
436 87 indvars - Number of aux indvars removed
437 25 instcombine - Number of dead inst eliminate
438 434 instcombine - Number of insts combined
439 248 licm - Number of load insts hoisted
440 1298 licm - Number of insts hoisted to a loop pre-header
441 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
442 75 mem2reg - Number of alloca's promoted
443 1444 cfgsimplify - Number of blocks simplified
444</pre><p>
445
446Obviously, with so many optimizations, having a unified framework for this stuff
447is very nice. Making your pass fit well into the framework makes it more
448maintainable and useful.<p>
449
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]450
Chris Lattnerb99344f2002-09-06 16:40:10 +0000[diff] [blame]451<!-- *********************************************************************** -->
452</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
453<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
454<a name="common">Helpful Hints for Common Operations
Chris Lattner986e0c92002-09-22 19:38:40 +0000[diff] [blame]455</b></font></td></tr></table><ul> <!--
456*********************************************************************** -->
Chris Lattnerb99344f2002-09-06 16:40:10 +0000[diff] [blame]457
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]458This section describes how to perform some very simple transformations of LLVM
459code. This is meant to give examples of common idioms used, showing the
460practical side of LLVM transformations.<p>
461
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]462Because this is a "how-to" section, you should also read about the main classes
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]463that you will be working with. The <a href="#coreclasses">Core LLVM Class
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]464Hierarchy Reference</a> contains details and descriptions of the main classes
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]465that you should know about.<p>
466
467<!-- NOTE: this section should be heavy on example code -->
468
469
470<!-- ======================================================================= -->
471</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
472<tr><td>&nbsp;</td><td width="100%">&nbsp;
473<font color="#EEEEFF" face="Georgia,Palatino"><b>
474<a name="inspection">Basic Inspection and Traversal Routines</a>
475</b></font></td></tr></table><ul>
476
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]477The LLVM compiler infrastructure have many different data structures that may be
478traversed. Following the example of the C++ standard template library, the
479techniques used to traverse these various data structures are all basically the
480same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
481method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
482function returns an iterator pointing to one past the last valid element of the
483sequence, and there is some <tt>XXXiterator</tt> data type that is common
484between the two operations.<p>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]485
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]486Because the pattern for iteration is common across many different aspects of the
487program representation, the standard template library algorithms may be used on
488them, and it is easier to remember how to iterate. First we show a few common
489examples of the data structures that need to be traversed. Other data
490structures are traversed in very similar ways.<p>
491
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]492
493<!-- _______________________________________________________________________ -->
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]494</ul><h4><a name="iterate_function"><hr size=0>Iterating over the <a
495href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
496href="#Function"><tt>Function</tt></a> </h4><ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]497
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]498It's quite common to have a <tt>Function</tt> instance that you'd like
499to transform in some way; in particular, you'd like to manipulate its
500<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over
501all of the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>.
502The following is an example that prints the name of a
503<tt>BasicBlock</tt> and the number of <tt>Instruction</tt>s it
504contains:
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]505
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]506<pre>
507 // func is a pointer to a Function instance
508 for(Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {
509
510 // print out the name of the basic block if it has one, and then the
511 // number of instructions that it contains
512
Joel Stanley72ef35e2002-09-06 23:05:12 +0000[diff] [blame]513 cerr &lt;&lt "Basic block (name=" &lt;&lt i-&gt;getName() &lt;&lt; ") has "
514 &lt;&lt i-&gt;size() &lt;&lt " instructions.\n";
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]515 }
516</pre>
517
518Note that i can be used as if it were a pointer for the purposes of
519invoking member functions of the <tt>Instruction</tt> class. This is
520because the indirection operator is overloaded for the iterator
521classes. In the above code, the expression <tt>i->size()</tt> is
522exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]523
524<!-- _______________________________________________________________________ -->
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]525</ul><h4><a name="iterate_basicblock"><hr size=0>Iterating over the <a
526href="#Instruction"><tt>Instruction</tt></a>s in a <a
527href="#BasicBlock"><tt>BasicBlock</tt></a> </h4><ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]528
Joel Stanleyaaeb1c12002-09-06 23:42:40 +0000[diff] [blame]529Just like when dealing with <tt>BasicBlock</tt>s in
530<tt>Function</tt>s, it's easy to iterate over the individual
531instructions that make up <tt>BasicBlock</tt>s. Here's a code snippet
532that prints out each instruction in a <tt>BasicBlock</tt>:
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]533
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]534<pre>
535 // blk is a pointer to a BasicBlock instance
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]536 for(BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Chris Lattner2b763062002-09-06 22:51:10 +0000[diff] [blame]537 // the next statement works since operator&lt;&lt;(ostream&amp;,...)
538 // is overloaded for Instruction&amp;
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]539 cerr &lt;&lt; *i &lt;&lt; "\n";
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]540</pre>
541
542However, this isn't really the best way to print out the contents of a
543<tt>BasicBlock</tt>! Since the ostream operators are overloaded for
544virtually anything you'll care about, you could have just invoked the
Chris Lattner2b763062002-09-06 22:51:10 +0000[diff] [blame]545print routine on the basic block itself: <tt>cerr &lt;&lt; *blk &lt;&lt;
546"\n";</tt>.<p>
547
548Note that currently operator&lt;&lt; is implemented for <tt>Value*</tt>, so it
549will print out the contents of the pointer, instead of
550the pointer value you might expect. This is a deprecated interface that will
551be removed in the future, so it's best not to depend on it. To print out the
552pointer value for now, you must cast to <tt>void*</tt>.<p>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]553
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]554
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]555<!-- _______________________________________________________________________ -->
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]556</ul><h4><a name="iterate_institer"><hr size=0>Iterating over the <a
557href="#Instruction"><tt>Instruction</tt></a>s in a <a
558href="#Function"><tt>Function</tt></a></h4><ul>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]559
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]560If you're finding that you commonly iterate over a <tt>Function</tt>'s
561<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s
562<tt>Instruction</tt>s, <tt>InstIterator</tt> should be used instead.
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]563You'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]564instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
565small example that shows how to dump all instructions in a function to
566stderr (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
567<tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&amp</tt>!):
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]568
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]569<pre>
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]570#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]571...
572// Suppose F is a ptr to a function
573for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
574 cerr &lt;&lt **i &lt;&lt "\n";
575</pre>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]576
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]577Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
578worklist with its initial contents. For example, if you wanted to
579initialize a worklist to contain all instructions in a
580<tt>Function</tt> F, all you would need to do is something like:
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]581
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]582<pre>
583std::set&lt;Instruction*&gt worklist;
584worklist.insert(inst_begin(F), inst_end(F));
585</pre>
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]586
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]587The STL set <tt>worklist</tt> would now contain all instructions in
588the <tt>Function</tt> pointed to by F.
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]589
590<!-- _______________________________________________________________________ -->
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]591</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]592pointer (and vice-versa) </h4><ul>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]593
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]594Sometimes, it'll be useful to grab a reference (or pointer) to a class
595instance when all you've got at hand is an iterator. Well, extracting
596a reference or a pointer from an iterator is very straightforward.
597Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and
598<tt>j</tt> is a <tt>BasicBlock::const_iterator</tt>:
599
600<pre>
Chris Lattner83b5ee02002-09-06 22:12:58 +0000[diff] [blame]601 Instruction&amp; inst = *i; // grab reference to instruction reference
602 Instruction* pinst = &amp;*i; // grab pointer to instruction reference
603 const Instruction&amp; inst = *j;
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]604</pre>
605However, the iterators you'll be working with in the LLVM framework
606are special: they will automatically convert to a ptr-to-instance type
607whenever they need to. Instead of dereferencing the iterator and then
608taking the address of the result, you can simply assign the iterator
609to the proper pointer type and you get the dereference and address-of
610operation as a result of the assignment (behind the scenes, this is a
611result of overloading casting mechanisms). Thus the last line of the
612last example,
613
Chris Lattner83b5ee02002-09-06 22:12:58 +0000[diff] [blame]614<pre>Instruction* pinst = &amp;*i;</pre>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]615
616is semantically equivalent to
617
618<pre>Instruction* pinst = i;</pre>
619
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]620It's also possible to turn a class pointer into the corresponding
621iterator. Usually, this conversion is quite inexpensive. The
622following code snippet illustrates use of the conversion constructors
623provided by LLVM iterators. By using these, you can explicitly grab
624the iterator of something without actually obtaining it via iteration
625over some structure:
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]626
627<pre>
628void printNextInstruction(Instruction* inst) {
629 BasicBlock::iterator it(inst);
630 ++it; // after this line, it refers to the instruction after *inst.
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]631 if(it != inst-&gt;getParent()->end()) cerr &lt;&lt; *it &lt;&lt; "\n";
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]632}
633</pre>
Joel Stanleyaaeb1c12002-09-06 23:42:40 +0000[diff] [blame]634Of course, this example is strictly pedagogical, because it'd be much
635better to explicitly grab the next instruction directly from inst.
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]636
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]637
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]638<!--_______________________________________________________________________-->
639</ul><h4><a name="iterate_complex"><hr size=0>Finding call sites: a slightly
640more complex example </h4><ul>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]641
642Say that you're writing a FunctionPass and would like to count all the
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]643locations in the entire module (that is, across every
Misha Brukman79223ed2003-07-28 19:21:20 +0000[diff] [blame^]644<tt>Function</tt>) where a certain function (i.e., some
645<tt>Function</tt>*) is already in scope. As you'll learn later, you may
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]646want to use an <tt>InstVisitor</tt> to accomplish this in a much more
647straightforward manner, but this example will allow us to explore how
648you'd do it if you didn't have <tt>InstVisitor</tt> around. In
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]649pseudocode, this is what we want to do:
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]650
651<pre>
652initialize callCounter to zero
653for each Function f in the Module
654 for each BasicBlock b in f
655 for each Instruction i in b
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]656 if(i is a CallInst and calls the given function)
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]657 increment callCounter
658</pre>
659
660And the actual code is (remember, since we're writing a
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]661<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]662has to override the <tt>runOnFunction</tt> method...):
663
664<pre>
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]665Function* targetFunc = ...;
666
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]667class OurFunctionPass : public FunctionPass {
668 public:
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]669 OurFunctionPass(): callCounter(0) { }
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]670
Chris Lattnercaa5d132002-09-09 19:58:18 +0000[diff] [blame]671 virtual runOnFunction(Function&amp; F) {
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]672 for(Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
673 for(BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
Chris Lattnera9030cb2002-09-16 22:08:07 +0000[diff] [blame]674 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]675 // we know we've encountered a call instruction, so we
676 // need to determine if it's a call to the
677 // function pointed to by m_func or not.
678
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]679 if(callInst-&gt;getCalledFunction() == targetFunc)
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]680 ++callCounter;
681 }
682 }
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]683 }
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]684
685 private:
Joel Stanleyd8aabb22002-09-09 16:29:58 +0000[diff] [blame]686 unsigned callCounter;
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]687};
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]688</pre>
689
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]690<!--_______________________________________________________________________-->
691</ul><h4><a name="iterate_chains"><hr size=0>Iterating over def-use &amp;
692use-def chains</h4><ul>
693
Joel Stanley01040b22002-09-11 20:50:04 +0000[diff] [blame]694Frequently, we might have an instance of the <a
695href="/doxygen/classValue.html">Value Class</a> and we want to
696determine which <tt>User</tt>s use the <tt>Value</tt>. The list of
697all <tt>User</tt>s of a particular <tt>Value</tt> is called a
698<i>def-use</i> chain. For example, let's say we have a
699<tt>Function*</tt> named <tt>F</tt> to a particular function
700<tt>foo</tt>. Finding all of the instructions that <i>use</i>
701<tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain of
702<tt>F</tt>:
703
704<pre>
705Function* F = ...;
706
707for(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]708 if(Instruction* Inst = dyn_cast&lt;Instruction&gt;(*i)) {
709 cerr &lt;&lt; "F is used in instruction:\n";
710 cerr &lt;&lt; *Inst &lt;&lt; "\n";
Joel Stanley01040b22002-09-11 20:50:04 +0000[diff] [blame]711 }
712}
713</pre>
714
715Alternately, it's common to have an instance of the <a
716href="/doxygen/classUser.html">User Class</a> and need to know what
717<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used
718by a <tt>User</tt> is known as a <i>use-def</i> chain. Instances of
719class <tt>Instruction</tt> are common <tt>User</tt>s, so we might want
720to iterate over all of the values that a particular instruction uses
721(that is, the operands of the particular <tt>Instruction</tt>):
722
723<pre>
724Instruction* pi = ...;
725
726for(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]727 Value* v = *i;
Joel Stanley01040b22002-09-11 20:50:04 +0000[diff] [blame]728 ...
729}
730</pre>
731
732
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]733<!--
734 def-use chains ("finding all users of"): Value::use_begin/use_end
735 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
736-->
737
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]738<!-- ======================================================================= -->
739</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
740<tr><td>&nbsp;</td><td width="100%">&nbsp;
741<font color="#EEEEFF" face="Georgia,Palatino"><b>
742<a name="simplechanges">Making simple changes</a>
743</b></font></td></tr></table><ul>
744
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]745There are some primitive transformation operations present in the LLVM
746infrastructure that are worth knowing about. When performing
747transformations, it's fairly common to manipulate the contents of
748basic blocks. This section describes some of the common methods for
749doing so and gives example code.
750
751<!--_______________________________________________________________________-->
752</ul><h4><a name="schanges_creating"><hr size=0>Creating and inserting
753 new <tt>Instruction</tt>s</h4><ul>
754
755<i>Instantiating Instructions</i>
756
757<p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
758constructor for the kind of instruction to instantiate and provide the
759necessary parameters. For example, an <tt>AllocaInst</tt> only
760<i>requires</i> a (const-ptr-to) <tt>Type</tt>. Thus:
761
762<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
763
764will create an <tt>AllocaInst</tt> instance that represents the
765allocation of one integer in the current stack frame, at runtime.
766Each <tt>Instruction</tt> subclass is likely to have varying default
767parameters which change the semantics of the instruction, so refer to
Chris Lattner4e1f96b2002-09-12 19:06:51 +0000[diff] [blame]768the <a href="/doxygen/classInstruction.html">doxygen documentation for
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]769the subclass of Instruction</a> that you're interested in
770instantiating.</p>
771
772<p><i>Naming values</i></p>
773
774<p>
775It is very useful to name the values of instructions when you're able
776to, as this facilitates the debugging of your transformations. If you
777end up looking at generated LLVM machine code, you definitely want to
778have logical names associated with the results of instructions! By
779supplying a value for the <tt>Name</tt> (default) parameter of the
780<tt>Instruction</tt> constructor, you associate a logical name with
781the result of the instruction's execution at runtime. For example,
782say that I'm writing a transformation that dynamically allocates space
783for an integer on the stack, and that integer is going to be used as
784some kind of index by some other code. To accomplish this, I place an
785<tt>AllocaInst</tt> at the first point in the first
786<tt>BasicBlock</tt> of some <tt>Function</tt>, and I'm intending to
787use it within the same <tt>Function</tt>. I might do:
788
789<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
790
791where <tt>indexLoc</tt> is now the logical name of the instruction's
792execution value, which is a pointer to an integer on the runtime
793stack.
794</p>
795
796<p><i>Inserting instructions</i></p>
797
798<p>
799There are essentially two ways to insert an <tt>Instruction</tt> into
800an existing sequence of instructions that form a <tt>BasicBlock</tt>:
801<ul>
802<li>Insertion into an explicit instruction list
803
804<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within
805that <tt>BasicBlock</tt>, and a newly-created instruction
806we wish to insert before <tt>*pi</tt>, we do the following:
807
808<pre>
809BasicBlock* pb = ...;
810Instruction* pi = ...;
811Instruction* newInst = new Instruction(...);
812pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb
813</pre>
814</p>
815
816<li>Insertion into an implicit instruction list
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]817<p><tt>Instruction</tt> instances that are already in
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]818<tt>BasicBlock</tt>s are implicitly associated with an existing
819instruction list: the instruction list of the enclosing basic block.
820Thus, we could have accomplished the same thing as the above code
821without being given a <tt>BasicBlock</tt> by doing:
822<pre>
823Instruction* pi = ...;
824Instruction* newInst = new Instruction(...);
825pi->getParent()->getInstList().insert(pi, newInst);
826</pre>
827In fact, this sequence of steps occurs so frequently that the
828<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes
829provide constructors which take (as a default parameter) a pointer to
830an <tt>Instruction</tt> which the newly-created <tt>Instruction</tt>
831should precede. That is, <tt>Instruction</tt> constructors are
832capable of inserting the newly-created instance into the
833<tt>BasicBlock</tt> of a provided instruction, immediately before that
834instruction. Using an <tt>Instruction</tt> constructor with a
835<tt>insertBefore</tt> (default) parameter, the above code becomes:
836<pre>
837Instruction* pi = ...;
838Instruction* newInst = new Instruction(..., pi);
839</pre>
840which is much cleaner, especially if you're creating a lot of
841instructions and adding them to <tt>BasicBlock</tt>s.
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]842 </p>
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]843</p>
Chris Lattner9ebf5162002-09-12 19:08:16 +0000[diff] [blame]844</ul>
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]845
846<!--_______________________________________________________________________-->
847</ul><h4><a name="schanges_deleting"><hr size=0>Deleting
Chris Lattner4e1f96b2002-09-12 19:06:51 +0000[diff] [blame]848<tt>Instruction</tt>s</h4><ul>
849
850Deleting an instruction from an existing sequence of instructions that form a <a
851href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First, you
852must have a pointer to the instruction that you wish to delete. Second, you
853need to obtain the pointer to that instruction's basic block. You use the
854pointer to the basic block to get its list of instructions and then use the
855erase function to remove your instruction.<p>
856
857For example:<p>
858
859<pre>
860 <a href="#Instruction">Instruction</a> *I = .. ;
Chris Lattner7dbf6832002-09-18 05:14:25 +0000[diff] [blame]861 <a href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();
862 BB-&gt;getInstList().erase(I);
Chris Lattner4e1f96b2002-09-12 19:06:51 +0000[diff] [blame]863</pre><p>
864
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]865<!--_______________________________________________________________________-->
866</ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
867 <tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
868
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]869<p><i>Replacing individual instructions</i></p>
870<p>
871Including "<a
Misha Brukman79223ed2003-07-28 19:21:20 +0000[diff] [blame^]872href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>" permits use of two very useful replace functions:
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]873<tt>ReplaceInstWithValue</tt> and <tt>ReplaceInstWithInst</tt>.
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]874
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]875<ul>
876
Chris Lattner7dbf6832002-09-18 05:14:25 +0000[diff] [blame]877<li><tt>ReplaceInstWithValue</tt>
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]878
879<p>This function replaces all uses (within a basic block) of a given
880instruction with a value, and then removes the original instruction.
881The following example illustrates the replacement of the result of a
882particular <tt>AllocaInst</tt> that allocates memory for a single
883integer with an null pointer to an integer.</p>
884
885<pre>
886AllocaInst* instToReplace = ...;
Joel Stanley4b287932002-09-29 17:31:54 +0000[diff] [blame]887BasicBlock::iterator ii(instToReplace);
888ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]889 Constant::getNullValue(PointerType::get(Type::IntTy)));
890</pre>
891
Chris Lattner7dbf6832002-09-18 05:14:25 +0000[diff] [blame]892<li><tt>ReplaceInstWithInst</tt>
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]893
894<p>This function replaces a particular instruction with another
895instruction. The following example illustrates the replacement of one
896<tt>AllocaInst</tt> with another.<p>
897
898<pre>
899AllocaInst* instToReplace = ...;
Joel Stanley4b287932002-09-29 17:31:54 +0000[diff] [blame]900BasicBlock::iterator ii(instToReplace);
901ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
Misha Brukmane7a7ab42003-05-07 21:47:39 +0000[diff] [blame]902 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]903</pre>
904
905</ul>
906<p><i>Replacing multiple uses of <tt>User</tt>s and
907 <tt>Value</tt>s</i></p>
908
909You can use <tt>Value::replaceAllUsesWith</tt> and
910<tt>User::replaceUsesOfWith</tt> to change more than one use at a
911time. See the doxygen documentation for the <a
912href="/doxygen/classValue.html">Value Class</a> and <a
913href="/doxygen/classUser.html">User Class</a>, respectively, for more
914information.
915
916<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
917include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
918ReplaceInstWithValue, ReplaceInstWithInst
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]919-->
Chris Lattnerb99344f2002-09-06 16:40:10 +0000[diff] [blame]920
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]921<!-- *********************************************************************** -->
922</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
923<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]924<a name="coreclasses">The Core LLVM Class Hierarchy Reference
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]925</b></font></td></tr></table><ul>
926<!-- *********************************************************************** -->
927
928The Core LLVM classes are the primary means of representing the program being
929inspected or transformed. The core LLVM classes are defined in header files in
930the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
931directory.<p>
932
933
934<!-- ======================================================================= -->
935</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
936<tr><td>&nbsp;</td><td width="100%">&nbsp;
937<font color="#EEEEFF" face="Georgia,Palatino"><b>
938<a name="Value">The <tt>Value</tt> class</a>
939</b></font></td></tr></table><ul>
940
941<tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
942doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
943
944
945The <tt>Value</tt> class is the most important class in LLVM Source base. It
946represents a typed value that may be used (among other things) as an operand to
947an instruction. There are many different types of <tt>Value</tt>s, such as <a
948href="#Constant"><tt>Constant</tt></a>s, <a
949href="#Argument"><tt>Argument</tt></a>s, and even <a
950href="#Instruction"><tt>Instruction</tt></a>s and <a
951href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
952
953A particular <tt>Value</tt> may be used many times in the LLVM representation
954for a program. For example, an incoming argument to a function (represented
955with an instance of the <a href="#Argument">Argument</a> class) is "used" by
956every instruction in the function that references the argument. To keep track
957of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
958href="#User"><tt>User</tt></a>s that is using it (the <a
959href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
960graph 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]961def-use information in the program, and is accessible through the <tt>use_</tt>*
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]962methods, shown below.<p>
963
964Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
965this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
966method. <a name="#nameWarning">In addition, all LLVM values can be named. The
967"name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
968
969<pre>
970 %<b>foo</b> = add int 1, 2
971</pre>
972
973The name of this instruction is "foo". <b>NOTE</b> that the name of any value
974may be missing (an empty string), so names should <b>ONLY</b> be used for
975debugging (making the source code easier to read, debugging printouts), they
976should not be used to keep track of values or map between them. For this
977purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
978instead.<p>
979
980One important aspect of LLVM is that there is no distinction between an SSA
981variable and the operation that produces it. Because of this, any reference to
982the value produced by an instruction (or the value available as an incoming
983argument, for example) is represented as a direct pointer to the class that
984represents this value. Although this may take some getting used to, it
985simplifies the representation and makes it easier to manipulate.<p>
986
987
988<!-- _______________________________________________________________________ -->
989</ul><h4><a name="m_Value"><hr size=0>Important Public Members of
990the <tt>Value</tt> class</h4><ul>
991
992<li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
993 <tt>Value::use_const_iterator</tt>
994 - Typedef for const_iterator over the use-list<br>
995 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
996 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
997 <tt>use_iterator use_begin()</tt>
998 - Get an iterator to the start of the use-list.<br>
999 <tt>use_iterator use_end()</tt>
1000 - Get an iterator to the end of the use-list.<br>
1001 <tt><a href="#User">User</a> *use_back()</tt>
1002 - Returns the last element in the list.<p>
1003
1004These 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>
1005
1006<li><tt><a href="#Type">Type</a> *getType() const</tt><p>
1007This method returns the Type of the Value.
1008
1009<li><tt>bool hasName() const</tt><br>
1010 <tt>std::string getName() const</tt><br>
1011 <tt>void setName(const std::string &amp;Name)</tt><p>
1012
1013This family of methods is used to access and assign a name to a <tt>Value</tt>,
1014be aware of the <a href="#nameWarning">precaution above</a>.<p>
1015
1016
1017<li><tt>void replaceAllUsesWith(Value *V)</tt><p>
1018
1019This method traverses the use list of a <tt>Value</tt> changing all <a
Misha Brukmanc4f5bb02002-09-18 02:21:57 +0000[diff] [blame]1020href="#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]1021instead. For example, if you detect that an instruction always produces a
1022constant value (for example through constant folding), you can replace all uses
1023of the instruction with the constant like this:<p>
1024
1025<pre>
1026 Inst-&gt;replaceAllUsesWith(ConstVal);
1027</pre><p>
1028
1029
1030
1031<!-- ======================================================================= -->
1032</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1033<tr><td>&nbsp;</td><td width="100%">&nbsp;
1034<font color="#EEEEFF" face="Georgia,Palatino"><b>
1035<a name="User">The <tt>User</tt> class</a>
1036</b></font></td></tr></table><ul>
1037
1038<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
1039doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
1040Superclass: <a href="#Value"><tt>Value</tt></a><p>
1041
1042
1043The <tt>User</tt> class is the common base class of all LLVM nodes that may
1044refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1045that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1046referring to. The <tt>User</tt> class itself is a subclass of
1047<tt>Value</tt>.<p>
1048
1049The operands of a <tt>User</tt> point directly to the LLVM <a
1050href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1051Single Assignment (SSA) form, there can only be one definition referred to,
1052allowing this direct connection. This connection provides the use-def
1053information in LLVM.<p>
1054
1055<!-- _______________________________________________________________________ -->
1056</ul><h4><a name="m_User"><hr size=0>Important Public Members of
1057the <tt>User</tt> class</h4><ul>
1058
1059The <tt>User</tt> class exposes the operand list in two ways: through an index
1060access interface and through an iterator based interface.<p>
1061
1062<li><tt>Value *getOperand(unsigned i)</tt><br>
1063 <tt>unsigned getNumOperands()</tt><p>
1064
1065These two methods expose the operands of the <tt>User</tt> in a convenient form
1066for direct access.<p>
1067
1068<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
1069 <tt>User::op_const_iterator</tt>
1070 <tt>use_iterator op_begin()</tt>
1071 - Get an iterator to the start of the operand list.<br>
1072 <tt>use_iterator op_end()</tt>
1073 - Get an iterator to the end of the operand list.<p>
1074
1075Together, these methods make up the iterator based interface to the operands of
1076a <tt>User</tt>.<p>
1077
1078
1079
1080<!-- ======================================================================= -->
1081</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1082<tr><td>&nbsp;</td><td width="100%">&nbsp;
1083<font color="#EEEEFF" face="Georgia,Palatino"><b>
1084<a name="Instruction">The <tt>Instruction</tt> class</a>
1085</b></font></td></tr></table><ul>
1086
1087<tt>#include "<a
1088href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
1089doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
1090Superclasses: <a href="#User"><tt>User</tt></a>, <a
1091href="#Value"><tt>Value</tt></a><p>
1092
1093The <tt>Instruction</tt> class is the common base class for all LLVM
1094instructions. It provides only a few methods, but is a very commonly used
1095class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1096opcode (instruction type) and the parent <a
1097href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1098into. To represent a specific type of instruction, one of many subclasses of
1099<tt>Instruction</tt> are used.<p>
1100
1101Because the <tt>Instruction</tt> class subclasses the <a
1102href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1103way as for other <a href="#User"><tt>User</tt></a>s (with the
1104<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1105<tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
1106
Chris Lattner17635252002-09-12 17:18:46 +0000[diff] [blame]1107An important file for the <tt>Instruction</tt> class is the
1108<tt>llvm/Instruction.def</tt> file. This file contains some meta-data about the
1109various different types of instructions in LLVM. It describes the enum values
1110that are used as opcodes (for example <tt>Instruction::Add</tt> and
1111<tt>Instruction::SetLE</tt>), as well as the concrete sub-classes of
1112<tt>Instruction</tt> that implement the instruction (for example <tt><a
1113href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1114href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1115this file confused doxygen, so these enum values don't show up correctly in the
1116<a href="/doxygen/classInstruction.html">doxygen output</a>.<p>
1117
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1118
1119<!-- _______________________________________________________________________ -->
1120</ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
1121the <tt>Instruction</tt> class</h4><ul>
1122
1123<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
1124
1125Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
1126<tt>Instruction</tt> is embedded into.<p>
1127
Chris Lattnerc3dc2122003-02-26 16:38:15 +0000[diff] [blame]1128<li><tt>bool mayWriteToMemory()</tt><p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1129
Chris Lattnerc3dc2122003-02-26 16:38:15 +0000[diff] [blame]1130Returns true if the instruction writes to memory, i.e. it is a <tt>call</tt>,
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1131<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
1132
1133<li><tt>unsigned getOpcode()</tt><p>
1134
1135Returns the opcode for the <tt>Instruction</tt>.<p>
1136
Chris Lattner17635252002-09-12 17:18:46 +0000[diff] [blame]1137<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt><p>
1138
1139Returns another instance of the specified instruction, identical in all ways to
1140the original except that the instruction has no parent (ie it's not embedded
1141into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>), and it has no name.<p>
1142
1143
1144
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1145<!--
1146
1147\subsection{Subclasses of Instruction :}
1148\begin{itemize}
1149<li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
1150 \begin{itemize}
1151 <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.
1152 \end{itemize}
1153<li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
1154 \begin{itemize}
1155 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
1156 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
1157 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
1158 \end{itemize}
1159
1160<li>PHINode : This represents the PHI instructions in the SSA form.
1161 \begin{itemize}
1162 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
1163 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
1164 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
1165 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
1166 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
1167 Add an incoming value to the end of the PHI list
1168 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
1169 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
1170 \end{itemize}
1171<li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
1172<li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
1173 \begin{itemize}
1174 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
1175 \end{itemize}
1176<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
1177 \begin{itemize}
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1178 <li><tt>Value * getPointerOperand()</tt>: Returns the Pointer Operand which is typically the 0th operand.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1179 \end{itemize}
1180<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
1181 \begin{itemize}
1182 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
1183 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
1184 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
1185 \end{itemize}
1186
1187\end{itemize}
1188
1189-->
1190
1191
1192<!-- ======================================================================= -->
1193</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1194<tr><td>&nbsp;</td><td width="100%">&nbsp;
1195<font color="#EEEEFF" face="Georgia,Palatino"><b>
1196<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1197</b></font></td></tr></table><ul>
1198
1199<tt>#include "<a
1200href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
1201doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
1202Superclass: <a href="#Value"><tt>Value</tt></a><p>
1203
1204
1205This class represents a single entry multiple exit section of the code, commonly
1206known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
1207maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
1208the body of the block. Matching the language definition, the last element of
1209this list of instructions is always a terminator instruction (a subclass of the
1210<a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
1211
1212In addition to tracking the list of instructions that make up the block, the
1213<tt>BasicBlock</tt> class also keeps track of the <a
1214href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
1215
1216Note that <tt>BasicBlock</tt>s themselves are <a
1217href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1218like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1219<tt>label</tt>.<p>
1220
1221
1222<!-- _______________________________________________________________________ -->
1223</ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
1224the <tt>BasicBlock</tt> class</h4><ul>
1225
1226<li><tt>BasicBlock(const std::string &amp;Name = "", <a
1227href="#Function">Function</a> *Parent = 0)</tt><p>
1228
1229The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1230insertion into a function. The constructor simply takes a name for the new
1231block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
1232into. If the <tt>Parent</tt> parameter is specified, the new
1233<tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
1234href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1235manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
1236
1237<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1238 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1239 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1240 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1241
1242These methods and typedefs are forwarding functions that have the same semantics
1243as the standard library methods of the same names. These methods expose the
1244underlying instruction list of a basic block in a way that is easy to
1245manipulate. To get the full complement of container operations (including
1246operations to update the list), you must use the <tt>getInstList()</tt>
1247method.<p>
1248
1249<li><tt>BasicBlock::InstListType &amp;getInstList()</tt><p>
1250
1251This method is used to get access to the underlying container that actually
1252holds the Instructions. This method must be used when there isn't a forwarding
1253function in the <tt>BasicBlock</tt> class for the operation that you would like
1254to perform. Because there are no forwarding functions for "updating"
1255operations, you need to use this if you want to update the contents of a
1256<tt>BasicBlock</tt>.<p>
1257
1258<li><tt><A href="#Function">Function</a> *getParent()</tt><p>
1259
1260Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1261embedded into, or a null pointer if it is homeless.<p>
1262
1263<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
1264
1265Returns a pointer to the terminator instruction that appears at the end of the
1266<tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1267instruction in the block is not a terminator, then a null pointer is
1268returned.<p>
1269
1270
1271<!-- ======================================================================= -->
1272</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1273<tr><td>&nbsp;</td><td width="100%">&nbsp;
1274<font color="#EEEEFF" face="Georgia,Palatino"><b>
1275<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1276</b></font></td></tr></table><ul>
1277
1278<tt>#include "<a
1279href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
1280doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
1281Superclasses: <a href="#User"><tt>User</tt></a>, <a
1282href="#Value"><tt>Value</tt></a><p>
1283
1284Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1285href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1286visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1287Because they are visible at global scope, they are also subject to linking with
1288other globals defined in different translation units. To control the linking
1289process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1290<tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
1291
1292If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1293<tt>static</tt> in C), it is not visible to code outside the current translation
1294unit, and does not participate in linking. If it has external linkage, it is
1295visible to external code, and does participate in linking. In addition to
1296linkage information, <tt>GlobalValue</tt>s keep track of which <a
1297href="#Module"><tt>Module</tt></a> they are currently part of.<p>
1298
1299Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
1300their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
1301always a pointer to its contents. This is explained in the LLVM Language
1302Reference Manual.<p>
1303
1304
1305<!-- _______________________________________________________________________ -->
1306</ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
1307the <tt>GlobalValue</tt> class</h4><ul>
1308
1309<li><tt>bool hasInternalLinkage() const</tt><br>
1310 <tt>bool hasExternalLinkage() const</tt><br>
1311 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
1312
1313These methods manipulate the linkage characteristics of the
1314<tt>GlobalValue</tt>.<p>
1315
1316<li><tt><a href="#Module">Module</a> *getParent()</tt><p>
1317
1318This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
1319currently embedded into.<p>
1320
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="Function">The <tt>Function</tt> class</a>
1328</b></font></td></tr></table><ul>
1329
1330<tt>#include "<a
1331href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
1332doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
1333Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1334href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1335
1336The <tt>Function</tt> class represents a single procedure in LLVM. It is
1337actually one of the more complex classes in the LLVM heirarchy because it must
1338keep track of a large amount of data. The <tt>Function</tt> class keeps track
1339of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
1340href="#Argument"><tt>Argument</tt></a>s, and a <a
1341href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
1342
1343The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
1344used part of <tt>Function</tt> objects. The list imposes an implicit ordering
1345of the blocks in the function, which indicate how the code will be layed out by
1346the backend. Additionally, the first <a
1347href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1348<tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
1349block. There are no implicit exit nodes, and in fact there may be multiple exit
1350nodes from a single <tt>Function</tt>. If the <a
1351href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1352the <tt>Function</tt> is actually a function declaration: the actual body of the
1353function hasn't been linked in yet.<p>
1354
1355In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1356<tt>Function</tt> class also keeps track of the list of formal <a
1357href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1358container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1359nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1360the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
1361
1362The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
1363feature that is only used when you have to look up a value by name. Aside from
1364that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
1365make sure that there are not conflicts between the names of <a
1366href="#Instruction"><tt>Instruction</tt></a>s, <a
1367href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1368href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
1369
1370
1371<!-- _______________________________________________________________________ -->
1372</ul><h4><a name="m_Function"><hr size=0>Important Public Members of
1373the <tt>Function</tt> class</h4><ul>
1374
1375<li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &amp;N = "")</tt><p>
1376
1377Constructor used when you need to create new <tt>Function</tt>s to add the the
1378program. The constructor must specify the type of the function to create and
1379whether or not it should start out with internal or external linkage.<p>
1380
1381<li><tt>bool isExternal()</tt><p>
1382
1383Return whether or not the <tt>Function</tt> has a body defined. If the function
1384is "external", it does not have a body, and thus must be resolved by linking
1385with a function defined in a different translation unit.<p>
1386
1387
1388<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
1389 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
1390 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1391 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1392
1393These are forwarding methods that make it easy to access the contents of a
1394<tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1395list.<p>
1396
1397<li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt><p>
1398
1399Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
1400neccesary to use when you need to update the list or perform a complex action
1401that doesn't have a forwarding method.<p>
1402
1403
1404<li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
1405 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
1406 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
1407 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
1408
1409These are forwarding methods that make it easy to access the contents of a
1410<tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
1411
1412<li><tt>Function::ArgumentListType &amp;getArgumentList()</tt><p>
1413
1414Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1415neccesary to use when you need to update the list or perform a complex action
1416that doesn't have a forwarding method.<p>
1417
1418
1419
1420<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
1421
1422Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1423function. Because the entry block for the function is always the first block,
1424this returns the first block of the <tt>Function</tt>.<p>
1425
1426<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1427 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
1428
1429This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
1430and returns the return type of the function, or the <a
1431href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
1432
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1433<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1434
1435Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
Chris Lattner6e6026b2002-11-20 18:36:02 +0000[diff] [blame]1436<tt>Function</tt>.<p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1437
1438
1439
1440<!-- ======================================================================= -->
1441</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1442<tr><td>&nbsp;</td><td width="100%">&nbsp;
1443<font color="#EEEEFF" face="Georgia,Palatino"><b>
1444<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1445</b></font></td></tr></table><ul>
1446
1447<tt>#include "<a
1448href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
1449doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
1450Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1451href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1452
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1453Global variables are represented with the (suprise suprise)
1454<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
1455also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
1456are always referenced by their address (global values must live in memory, so
1457their "name" refers to their address). Global variables may have an initial
1458value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
1459have an initializer, they may be marked as "constant" themselves (indicating
1460that their contents never change at runtime).<p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1461
1462
1463<!-- _______________________________________________________________________ -->
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1464</ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
1465<tt>GlobalVariable</tt> class</h4><ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1466
1467<li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
1468isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
1469&amp;Name = "")</tt><p>
1470
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1471Create a new global variable of the specified type. If <tt>isConstant</tt> is
1472true then the global variable will be marked as unchanging for the program, and
1473if <tt>isInternal</tt> is true the resultant global variable will have internal
1474linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
1475
1476
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1477<li><tt>bool isConstant() const</tt><p>
1478
1479Returns true if this is a global variable is known not to be modified at
1480runtime.<p>
1481
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1482
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1483<li><tt>bool hasInitializer()</tt><p>
1484
1485Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
1486
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1487
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1488<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
1489
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1490Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
1491this method if there is no initializer.<p>
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="Module">The <tt>Module</tt> class</a>
1499</b></font></td></tr></table><ul>
1500
1501<tt>#include "<a
1502href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
1503doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
1504
1505The <tt>Module</tt> class represents the top level structure present in LLVM
1506programs. An LLVM module is effectively either a translation unit of the
1507original program or a combination of several translation units merged by the
1508linker. The <tt>Module</tt> class keeps track of a list of <a
1509href="#Function"><tt>Function</tt></a>s, a list of <a
1510href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1511href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1512helpful member functions that try to make common operations easy.<p>
1513
1514
1515<!-- _______________________________________________________________________ -->
1516</ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
1517<tt>Module</tt> class</h4><ul>
1518
1519<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
1520 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
1521 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1522 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1523
1524These are forwarding methods that make it easy to access the contents of a
1525<tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1526list.<p>
1527
1528<li><tt>Module::FunctionListType &amp;getFunctionList()</tt><p>
1529
1530Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1531neccesary to use when you need to update the list or perform a complex action
1532that doesn't have a forwarding method.<p>
1533
1534<!-- Global Variable -->
1535<hr size=0>
1536
1537<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
1538 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
1539 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
1540 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
1541
1542These are forwarding methods that make it easy to access the contents of a
1543<tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
1544list.<p>
1545
1546<li><tt>Module::GlobalListType &amp;getGlobalList()</tt><p>
1547
1548Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
1549This is neccesary to use when you need to update the list or perform a complex
1550action that doesn't have a forwarding method.<p>
1551
1552
1553<!-- Symbol table stuff -->
1554<hr size=0>
1555
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1556<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1557
Chris Lattner6e6026b2002-11-20 18:36:02 +0000[diff] [blame]1558Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for
1559this <tt>Module</tt>.<p>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]1560
1561
1562<!-- Convenience methods -->
1563<hr size=0>
1564
1565<li><tt><a href="#Function">Function</a> *getFunction(const std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
1566
1567Look up the specified function in the <tt>Module</tt> <a
1568href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
1569<tt>null</tt>.<p>
1570
1571
1572<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
1573 &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
1574
1575Look up the specified function in the <tt>Module</tt> <a
1576href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
1577external declaration for the function and return it.<p>
1578
1579
1580<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
1581
1582If there is at least one entry in the <a
1583href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
1584href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
1585string.<p>
1586
1587
1588<li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
1589*Ty)</tt><p>
1590
1591Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
1592<tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
1593is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
1594modified.<p>
1595
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1596
1597<!-- ======================================================================= -->
1598</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1599<tr><td>&nbsp;</td><td width="100%">&nbsp;
1600<font color="#EEEEFF" face="Georgia,Palatino"><b>
1601<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
1602</b></font></td></tr></table><ul>
1603
1604Constant represents a base class for different types of constants. It is
1605subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
1606ConstantArray etc for representing the various types of Constants.<p>
1607
1608
1609<!-- _______________________________________________________________________ -->
1610</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1611
1612<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
1613
1614
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1615<hr>
1616Important Subclasses of Constant<p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1617
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1618<ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1619<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1620<ul>
1621 <li><tt>int64_t getValue() const</tt>: Returns the underlying value of this constant.
1622</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1623<li>ConstantUInt : This class represents an unsigned integer.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1624<ul>
1625 <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of this constant.
1626</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1627<li>ConstantFP : This class represents a floating point constant.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1628<ul>
1629 <li><tt>double getValue() const</tt>: Returns the underlying value of this constant.
1630</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1631<li>ConstantBool : This represents a boolean constant.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1632<ul>
1633 <li><tt>bool getValue() const</tt>: Returns the underlying value of this constant.
1634</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1635<li>ConstantArray : This represents a constant array.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1636<ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1637 <li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1638</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1639<li>ConstantStruct : This represents a constant struct.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1640<ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1641 <li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1642</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1643<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1644<ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1645<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1646</ul>
1647</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1648
1649
1650<!-- ======================================================================= -->
1651</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1652<tr><td>&nbsp;</td><td width="100%">&nbsp;
1653<font color="#EEEEFF" face="Georgia,Palatino"><b>
1654<a name="Type">The <tt>Type</tt> class and Derived Types</a>
1655</b></font></td></tr></table><ul>
1656
1657Type as noted earlier is also a subclass of a Value class. Any primitive
1658type (like int, short etc) in LLVM is an instance of Type Class. All
1659other types are instances of subclasses of type like FunctionType,
1660ArrayType etc. DerivedType is the interface for all such dervied types
1661including FunctionType, ArrayType, PointerType, StructType. Types can have
1662names. They can be recursive (StructType). There exists exactly one instance
1663of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
1664
1665<!-- _______________________________________________________________________ -->
1666</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1667
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1668<li><tt>PrimitiveID getPrimitiveID() const</tt>: Returns the base type of the type.
1669<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.
1670<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.
1671<li><tt> bool isInteger() const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
1672<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.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1673
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1674<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two floating point types.
1675<li><tt>bool isRecursive() const</tt>: Returns rue if the type graph contains a cycle.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1676<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.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1677<li><tt>bool isPrimitiveType() const</tt>: Returns true if it is a primitive type.
1678<li><tt>bool isDerivedType() const</tt>: Returns true if it is a derived type.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1679<li><tt>const Type * getContainedType (unsigned i) const</tt>:
1680This 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.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1681<li><tt>unsigned getNumContainedTypes() const</tt>: Return the number of types in the derived type.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1682
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1683<p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1684
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1685<hr>
1686Derived Types<p>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1687
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1688<ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1689<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1690<ul>
1691 <li><tt>const Type * getElementType() const</tt>: Returns the type of each of the elements in the sequential type.
1692</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1693<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1694<ul>
1695 <li><tt>unsigned getNumElements() const</tt>: Returns the number of elements in the array.
1696</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1697<li>PointerType : Subclass of SequentialType for pointer types.
1698<li>StructType : subclass of DerivedTypes for struct types
1699<li>FunctionType : subclass of DerivedTypes for function types.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1700
1701<ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1702
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1703 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg function
1704 <li><tt> const Type * getReturnType() const</tt>: Returns the return type of the function.
1705 <li><tt> const ParamTypes &amp;getParamTypes() const</tt>: Returns a vector of parameter types.
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1706 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]1707 <li><tt> const unsigned getNumParams() const</tt>: Returns the number of formal parameters.
1708</ul>
1709</ul>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1710
1711
1712
1713
1714<!-- ======================================================================= -->
1715</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1716<tr><td>&nbsp;</td><td width="100%">&nbsp;
1717<font color="#EEEEFF" face="Georgia,Palatino"><b>
1718<a name="Argument">The <tt>Argument</tt> class</a>
1719</b></font></td></tr></table><ul>
1720
1721This subclass of Value defines the interface for incoming formal arguments to a
1722function. A Function maitanis a list of its formal arguments. An argument has a
1723pointer to the parent Function.
1724
1725
1726
1727
1728<!-- *********************************************************************** -->
1729</ul>
1730<!-- *********************************************************************** -->
1731
1732<hr><font size-1>
1733<address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
1734<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
1735<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
1736<!-- hhmts start -->
Chris Lattner6a547102003-04-23 16:26:15 +0000[diff] [blame]1737Last modified: Wed Apr 23 11:21:57 CDT 2003
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1738<!-- hhmts end -->
1739</font></body></html>