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7 <tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM Programmer's Manual</b></font></td>
11 <li><a href="#introduction">Introduction</a>
12 <li><a href="#general">General Information</a>
14 <li><a href="#stl">The C++ Standard Template Library</a>
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
21 <li><a href="#apis">Important and useful LLVM APIs</a>
23 <li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt> and
24 <tt>dyn_cast<></tt> templates</a>
25 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro &
26 <tt>-debug</tt> option</a>
27 <li><a href="#Statistic">The <tt>Statistic</tt> template &
28 <tt>-stats</tt> option</a>
30 <li>The <tt>InstVisitor</tt> template
31 <li>The general graph API
34 <li><a href="#common">Helpful Hints for Common Operations</a>
36 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
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>
42 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
43 in a <tt>Function</tt></a>
44 <li><a href="#iterate_convert">Turning an iterator into a class
46 <li><a href="#iterate_complex">Finding call sites: a more complex
48 <li><a href="#iterate_chains">Iterating over def-use & use-def
51 <li><a href="#simplechanges">Making simple changes</a>
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>
61 <li>Working with the Control Flow Graph
63 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
69 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
71 <li><a href="#Value">The <tt>Value</tt> class</a>
73 <li><a href="#User">The <tt>User</tt> class</a>
75 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
79 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
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>
85 <li><a href="#Module">The <tt>Module</tt> class</a>
86 <li><a href="#Constant">The <tt>Constant</tt> class</a>
92 <li><a href="#Type">The <tt>Type</tt> class</a>
93 <li><a href="#Argument">The <tt>Argument</tt> class</a>
95 <li>The <tt>SymbolTable</tt> class
96 <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
98 <li>Creating, inserting, moving and deleting from LLVM lists
100 <li>Important iterator invalidation semantics to be aware of
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
105 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a></b><p>
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 <!-- *********************************************************************** -->
116 This document is meant to highlight some of the important classes and interfaces
117 available in the LLVM source-base. This manual is not intended to explain what
118 LLVM is, how it works, and what LLVM code looks like. It assumes that you know
119 the basics of LLVM and are interested in writing transformations or otherwise
120 analyzing or manipulating the code.<p>
122 This document should get you oriented so that you can find your way in the
123 continuously growing source code that makes up the LLVM infrastructure. Note
124 that this manual is not intended to serve as a replacement for reading the
125 source code, so if you think there should be a method in one of these classes to
126 do something, but it's not listed, check the source. Links to the <a
127 href="/doxygen/">doxygen</a> sources are provided to make this as easy as
130 The first section of this document describes general information that is useful
131 to know when working in the LLVM infrastructure, and the second describes the
132 Core LLVM classes. In the future this manual will be extended with information
133 describing how to use extension libraries, such as dominator information, CFG
134 traversal routines, and useful utilities like the <tt><a
135 href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
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 <!-- *********************************************************************** -->
145 This section contains general information that is useful if you are working in
146 the LLVM source-base, but that isn't specific to any particular API.<p>
149 <!-- ======================================================================= -->
150 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
151 <tr><td> </td><td width="100%">
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>
156 LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
157 more than you are used to, or have seen before. Because of this, you might want
158 to do a little background reading in the techniques used and capabilities of the
159 library. There are many good pages that discuss the STL, and several books on
160 the subject that you can get, so it will not be discussed in this document.<p>
162 Here are some useful links:<p>
164 <li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++
165 Library reference</a> - an excellent reference for the STL and other parts of
166 the standard C++ library.
168 <li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
169 O'Reilly book in the making. It has a decent <a
170 href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
171 Reference</a> that rivals Dinkumware's, and is actually free until the book is
174 <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
177 <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
179 href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
182 <li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
187 You are also encouraged to take a look at the <a
188 href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
189 to write maintainable code more than where to put your curly braces.<p>
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 <!-- *********************************************************************** -->
199 Here we highlight some LLVM APIs that are generally useful and good to know
200 about when writing transformations.<p>
202 <!-- ======================================================================= -->
203 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
204 <tr><td> </td><td width="100%">
205 <font color="#EEEEFF" face="Georgia,Palatino"><b>
206 <a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
207 </b></font></td></tr></table><ul>
209 The LLVM source-base makes extensive use of a custom form of RTTI. These
210 templates have many similarities to the C++ <tt>dynamic_cast<></tt>
211 operator, but they don't have some drawbacks (primarily stemming from the fact
212 that <tt>dynamic_cast<></tt> only works on classes that have a v-table).
213 Because they are used so often, you must know what they do and how they work.
214 All of these templates are defined in the <a
215 href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a> file (note
216 that you very rarely have to include this file directly).<p>
220 <dt><tt>isa<></tt>:
222 <dd>The <tt>isa<></tt> operator works exactly like the Java
223 "<tt>instanceof</tt>" operator. It returns true or false depending on whether a
224 reference or pointer points to an instance of the specified class. This can be
225 very useful for constraint checking of various sorts (example below).<p>
228 <dt><tt>cast<></tt>:
230 <dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
231 converts a pointer or reference from a base class to a derived cast, causing an
232 assertion failure if it is not really an instance of the right type. This
233 should be used in cases where you have some information that makes you believe
234 that something is of the right type. An example of the <tt>isa<></tt> and
235 <tt>cast<></tt> template is:<p>
238 static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
239 if (isa<<a href="#Constant">Constant</a>>(V) || isa<<a href="#Argument">Argument</a>>(V) || isa<<a href="#GlobalValue">GlobalValue</a>>(V))
242 <i>// Otherwise, it must be an instruction...</i>
243 return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
246 Note that you should <b>not</b> use an <tt>isa<></tt> test followed by a
247 <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt> operator.<p>
250 <dt><tt>dyn_cast<></tt>:
252 <dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
253 checks to see if the operand is of the specified type, and if so, returns a
254 pointer to it (this operator does not work with references). If the operand is
255 not of the correct type, a null pointer is returned. Thus, this works very much
256 like the <tt>dynamic_cast</tt> operator in C++, and should be used in the same
257 circumstances. Typically, the <tt>dyn_cast<></tt> operator is used in an
258 <tt>if</tt> statement or some other flow control statement like this:<p>
261 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
266 This form of the <tt>if</tt> statement effectively combines together a call to
267 <tt>isa<></tt> and a call to <tt>cast<></tt> into one statement,
268 which is very convenient.<p>
270 Another common example is:<p>
273 <i>// Loop over all of the phi nodes in a basic block</i>
274 BasicBlock::iterator BBI = BB->begin();
275 for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(&*BBI); ++BBI)
279 Note that the <tt>dyn_cast<></tt> operator, like C++'s
280 <tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused. In
281 particular you should not use big chained <tt>if/then/else</tt> blocks to check
282 for lots of different variants of classes. If you find yourself wanting to do
283 this, it is much cleaner and more efficient to use the InstVisitor class to
284 dispatch over the instruction type directly.<p>
287 <dt><tt>cast_or_null<></tt>:
289 <dd>The <tt>cast_or_null<></tt> operator works just like the
290 <tt>cast<></tt> operator, except that it allows for a null pointer as an
291 argument (which it then propagates). This can sometimes be useful, allowing you
292 to combine several null checks into one.<p>
295 <dt><tt>dyn_cast_or_null<></tt>:
297 <dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
298 <tt>dyn_cast<></tt> operator, except that it allows for a null pointer as
299 an argument (which it then propagates). This can sometimes be useful, allowing
300 you to combine several null checks into one.<p>
304 These five templates can be used with any classes, whether they have a v-table
305 or 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.
307 Describing this is currently outside the scope of this document, but there are
308 lots of examples in the LLVM source base.<p>
311 <!-- ======================================================================= -->
312 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
313 <tr><td> </td><td width="100%">
314 <font color="#EEEEFF" face="Georgia,Palatino"><b>
315 <a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
316 </b></font></td></tr></table><ul>
318 Often when working on your pass you will put a bunch of debugging printouts and
319 other code into your pass. After you get it working, you want to remove
320 it... but you may need it again in the future (to work out new bugs that you run
323 Naturally, because of this, you don't want to delete the debug printouts, but
324 you don't want them to always be noisy. A standard compromise is to comment
325 them out, allowing you to enable them if you need them in the future.<p>
328 href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>"
329 file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
330 this 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:
336 DEBUG(std::cerr << "I am here!\n");
340 Then you can run your pass like this:<p>
343 $ opt < a.bc > /dev/null -mypass
345 $ opt < a.bc > /dev/null -mypass -debug
350 Using the <tt>DEBUG()</tt> macro instead of a home brewed solution allows you to
351 now have to create "yet another" command line option for the debug output for
352 your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
353 so they do not cause a performance impact at all (for the same reason, they
354 should also not contain side-effects!).<p>
356 One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
357 enable 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
359 program hasn't been started yet, you can always just run it with
363 <!-- ======================================================================= -->
364 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
365 <tr><td> </td><td width="100%">
366 <font color="#EEEEFF" face="Georgia,Palatino"><b>
367 <a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
369 </b></font></td></tr></table><ul>
372 href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>"
373 file provides a template named <tt>Statistic</tt> that is used as a unified way
374 to keeping track of what the LLVM compiler is doing and how effective various
375 optimizations are. It is useful to see what optimizations are contributing to
376 making a particular program run faster.<p>
378 Often you may run your pass on some big program, and you're interested to see
379 how many times it makes a certain transformation. Although you can do this with
380 hand inspection, or some ad-hoc method, this is a real pain and not very useful
381 for big programs. Using the <tt>Statistic</tt> template makes it very easy to
382 keep track of this information, and the calculated information is presented in a
383 uniform manner with the rest of the passes being executed.<p>
385 There are many examples of <tt>Statistic</tt> users, but this basics of using it
389 <li>Define your statistic like this:<p>
392 static Statistic<> NumXForms("mypassname", "The # of times I did stuff");
395 The <tt>Statistic</tt> template can emulate just about any data-type, but if you
396 do not specify a template argument, it defaults to acting like an unsigned int
397 counter (this is usually what you want).<p>
399 <li>Whenever you make a transformation, bump the counter:<p>
402 ++NumXForms; // I did stuff
407 That's all you have to do. To get '<tt>opt</tt>' to print out the statistics
408 gathered, use the '<tt>-stats</tt>' option:<p>
411 $ opt -stats -mypassname < program.bc > /dev/null
412 ... statistic output ...
415 When running <tt>gccas</tt> on a C file from the SPEC benchmark suite, it gives
416 a report that looks like this:<p>
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
446 Obviously, with so many optimizations, having a unified framework for this stuff
447 is very nice. Making your pass fit well into the framework makes it more
448 maintainable and useful.<p>
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
455 </b></font></td></tr></table><ul> <!--
456 *********************************************************************** -->
458 This section describes how to perform some very simple transformations of LLVM
459 code. This is meant to give examples of common idioms used, showing the
460 practical side of LLVM transformations.<p>
462 Because this is a "how-to" section, you should also read about the main classes
463 that you will be working with. The <a href="#coreclasses">Core LLVM Class
464 Hierarchy Reference</a> contains details and descriptions of the main classes
465 that you should know about.<p>
467 <!-- NOTE: this section should be heavy on example code -->
470 <!-- ======================================================================= -->
471 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
472 <tr><td> </td><td width="100%">
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>
477 The LLVM compiler infrastructure have many different data structures that may be
478 traversed. Following the example of the C++ standard template library, the
479 techniques used to traverse these various data structures are all basically the
480 same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
481 method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
482 function returns an iterator pointing to one past the last valid element of the
483 sequence, and there is some <tt>XXXiterator</tt> data type that is common
484 between the two operations.<p>
486 Because the pattern for iteration is common across many different aspects of the
487 program representation, the standard template library algorithms may be used on
488 them, and it is easier to remember how to iterate. First we show a few common
489 examples of the data structures that need to be traversed. Other data
490 structures are traversed in very similar ways.<p>
493 <!-- _______________________________________________________________________ -->
494 </ul><h4><a name="iterate_function"><hr size=0>Iterating over the <a
495 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
496 href="#Function"><tt>Function</tt></a> </h4><ul>
498 It's quite common to have a <tt>Function</tt> instance that you'd like
499 to 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
501 all of the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>.
502 The following is an example that prints the name of a
503 <tt>BasicBlock</tt> and the number of <tt>Instruction</tt>s it
507 // func is a pointer to a Function instance
508 for(Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {
510 // print out the name of the basic block if it has one, and then the
511 // number of instructions that it contains
513 cerr << "Basic block (name=" << i->getName() << ") has "
514 << i->size() << " instructions.\n";
518 Note that i can be used as if it were a pointer for the purposes of
519 invoking member functions of the <tt>Instruction</tt> class. This is
520 because the indirection operator is overloaded for the iterator
521 classes. In the above code, the expression <tt>i->size()</tt> is
522 exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.
524 <!-- _______________________________________________________________________ -->
525 </ul><h4><a name="iterate_basicblock"><hr size=0>Iterating over the <a
526 href="#Instruction"><tt>Instruction</tt></a>s in a <a
527 href="#BasicBlock"><tt>BasicBlock</tt></a> </h4><ul>
529 Just like when dealing with <tt>BasicBlock</tt>s in
530 <tt>Function</tt>s, it's easy to iterate over the individual
531 instructions that make up <tt>BasicBlock</tt>s. Here's a code snippet
532 that prints out each instruction in a <tt>BasicBlock</tt>:
535 // blk is a pointer to a BasicBlock instance
536 for(BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
537 // the next statement works since operator<<(ostream&,...)
538 // is overloaded for Instruction&
539 cerr << *i << "\n";
542 However, 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
544 virtually anything you'll care about, you could have just invoked the
545 print routine on the basic block itself: <tt>cerr << *blk <<
548 Note that currently operator<< is implemented for <tt>Value*</tt>, so it
549 will print out the contents of the pointer, instead of
550 the pointer value you might expect. This is a deprecated interface that will
551 be removed in the future, so it's best not to depend on it. To print out the
552 pointer value for now, you must cast to <tt>void*</tt>.<p>
555 <!-- _______________________________________________________________________ -->
556 </ul><h4><a name="iterate_institer"><hr size=0>Iterating over the <a
557 href="#Instruction"><tt>Instruction</tt></a>s in a <a
558 href="#Function"><tt>Function</tt></a></h4><ul>
560 If 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.
563 You'll need to include <a href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>, and then
564 instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
565 small example that shows how to dump all instructions in a function to
566 stderr (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
567 <tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&</tt>!):
570 #include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
572 // Suppose F is a ptr to a function
573 for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
574 cerr << **i << "\n";
577 Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
578 worklist with its initial contents. For example, if you wanted to
579 initialize a worklist to contain all instructions in a
580 <tt>Function</tt> F, all you would need to do is something like:
583 std::set<Instruction*> worklist;
584 worklist.insert(inst_begin(F), inst_end(F));
587 The STL set <tt>worklist</tt> would now contain all instructions in
588 the <tt>Function</tt> pointed to by F.
590 <!-- _______________________________________________________________________ -->
591 </ul><h4><a name="iterate_convert"><hr size=0>Turning an iterator into a class
592 pointer (and vice-versa) </h4><ul>
594 Sometimes, it'll be useful to grab a reference (or pointer) to a class
595 instance when all you've got at hand is an iterator. Well, extracting
596 a reference or a pointer from an iterator is very straightforward.
597 Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and
598 <tt>j</tt> is a <tt>BasicBlock::const_iterator</tt>:
601 Instruction& inst = *i; // grab reference to instruction reference
602 Instruction* pinst = &*i; // grab pointer to instruction reference
603 const Instruction& inst = *j;
605 However, the iterators you'll be working with in the LLVM framework
606 are special: they will automatically convert to a ptr-to-instance type
607 whenever they need to. Instead of dereferencing the iterator and then
608 taking the address of the result, you can simply assign the iterator
609 to the proper pointer type and you get the dereference and address-of
610 operation as a result of the assignment (behind the scenes, this is a
611 result of overloading casting mechanisms). Thus the last line of the
614 <pre>Instruction* pinst = &*i;</pre>
616 is semantically equivalent to
618 <pre>Instruction* pinst = i;</pre>
620 <b>Caveat emptor</b>: The above syntax works <i>only</i> when you're <i>not</i>
621 working with <tt>dyn_cast</tt>. The template definition of <tt><a
622 href="#isa">dyn_cast</a></tt> isn't implemented to handle this yet, so you'll
623 still need the following in order for things to work properly:
626 BasicBlock::iterator bbi = ...;
627 <a href="#BranchInst">BranchInst</a>* b = <a href="#isa">dyn_cast</a><<a href="#BranchInst">BranchInst</a>>(&*bbi);
630 It's also possible to turn a class pointer into the corresponding
631 iterator. Usually, this conversion is quite inexpensive. The
632 following code snippet illustrates use of the conversion constructors
633 provided by LLVM iterators. By using these, you can explicitly grab
634 the iterator of something without actually obtaining it via iteration
638 void printNextInstruction(Instruction* inst) {
639 BasicBlock::iterator it(inst);
640 ++it; // after this line, it refers to the instruction after *inst.
641 if(it != inst->getParent()->end()) cerr << *it << "\n";
644 Of course, this example is strictly pedagogical, because it'd be much
645 better to explicitly grab the next instruction directly from inst.
648 <!--_______________________________________________________________________-->
649 </ul><h4><a name="iterate_complex"><hr size=0>Finding call sites: a slightly
650 more complex example </h4><ul>
652 Say that you're writing a FunctionPass and would like to count all the
653 locations in the entire module (that is, across every
654 <tt>Function</tt>) where a certain function (i.e. some
655 <tt>Function</tt>*) already in scope. As you'll learn later, you may
656 want to use an <tt>InstVisitor</tt> to accomplish this in a much more
657 straightforward manner, but this example will allow us to explore how
658 you'd do it if you didn't have <tt>InstVisitor</tt> around. In
659 pseudocode, this is what we want to do:
662 initialize callCounter to zero
663 for each Function f in the Module
664 for each BasicBlock b in f
665 for each Instruction i in b
666 if(i is a CallInst and calls the given function)
667 increment callCounter
670 And the actual code is (remember, since we're writing a
671 <tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply
672 has to override the <tt>runOnFunction</tt> method...):
675 Function* targetFunc = ...;
677 class OurFunctionPass : public FunctionPass {
679 OurFunctionPass(): callCounter(0) { }
681 virtual runOnFunction(Function& F) {
682 for(Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
683 for(BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {
684 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a href="#CallInst">CallInst</a>>(&*i)) {
685 // we know we've encountered a call instruction, so we
686 // need to determine if it's a call to the
687 // function pointed to by m_func or not.
689 if(callInst->getCalledFunction() == targetFunc)
696 unsigned callCounter;
700 <!--_______________________________________________________________________-->
701 </ul><h4><a name="iterate_chains"><hr size=0>Iterating over def-use &
702 use-def chains</h4><ul>
704 Frequently, we might have an instance of the <a
705 href="/doxygen/classValue.html">Value Class</a> and we want to
706 determine which <tt>User</tt>s use the <tt>Value</tt>. The list of
707 all <tt>User</tt>s of a particular <tt>Value</tt> is called a
708 <i>def-use</i> chain. For example, let's say we have a
709 <tt>Function*</tt> named <tt>F</tt> to a particular function
710 <tt>foo</tt>. Finding all of the instructions that <i>use</i>
711 <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain of
717 for(Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {
718 if(Instruction* Inst = dyn_cast<Instruction>(*i)) {
719 cerr << "F is used in instruction:\n";
720 cerr << *Inst << "\n";
725 Alternately, it's common to have an instance of the <a
726 href="/doxygen/classUser.html">User Class</a> and need to know what
727 <tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used
728 by a <tt>User</tt> is known as a <i>use-def</i> chain. Instances of
729 class <tt>Instruction</tt> are common <tt>User</tt>s, so we might want
730 to iterate over all of the values that a particular instruction uses
731 (that is, the operands of the particular <tt>Instruction</tt>):
734 Instruction* pi = ...;
736 for(User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {
744 def-use chains ("finding all users of"): Value::use_begin/use_end
745 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
748 <!-- ======================================================================= -->
749 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
750 <tr><td> </td><td width="100%">
751 <font color="#EEEEFF" face="Georgia,Palatino"><b>
752 <a name="simplechanges">Making simple changes</a>
753 </b></font></td></tr></table><ul>
755 There are some primitive transformation operations present in the LLVM
756 infrastructure that are worth knowing about. When performing
757 transformations, it's fairly common to manipulate the contents of
758 basic blocks. This section describes some of the common methods for
759 doing so and gives example code.
761 <!--_______________________________________________________________________-->
762 </ul><h4><a name="schanges_creating"><hr size=0>Creating and inserting
763 new <tt>Instruction</tt>s</h4><ul>
765 <i>Instantiating Instructions</i>
767 <p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
768 constructor for the kind of instruction to instantiate and provide the
769 necessary parameters. For example, an <tt>AllocaInst</tt> only
770 <i>requires</i> a (const-ptr-to) <tt>Type</tt>. Thus:
772 <pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
774 will create an <tt>AllocaInst</tt> instance that represents the
775 allocation of one integer in the current stack frame, at runtime.
776 Each <tt>Instruction</tt> subclass is likely to have varying default
777 parameters which change the semantics of the instruction, so refer to
778 the <a href="/doxygen/classInstruction.html">doxygen documentation for
779 the subclass of Instruction</a> that you're interested in
782 <p><i>Naming values</i></p>
785 It is very useful to name the values of instructions when you're able
786 to, as this facilitates the debugging of your transformations. If you
787 end up looking at generated LLVM machine code, you definitely want to
788 have logical names associated with the results of instructions! By
789 supplying a value for the <tt>Name</tt> (default) parameter of the
790 <tt>Instruction</tt> constructor, you associate a logical name with
791 the result of the instruction's execution at runtime. For example,
792 say that I'm writing a transformation that dynamically allocates space
793 for an integer on the stack, and that integer is going to be used as
794 some kind of index by some other code. To accomplish this, I place an
795 <tt>AllocaInst</tt> at the first point in the first
796 <tt>BasicBlock</tt> of some <tt>Function</tt>, and I'm intending to
797 use it within the same <tt>Function</tt>. I might do:
799 <pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
801 where <tt>indexLoc</tt> is now the logical name of the instruction's
802 execution value, which is a pointer to an integer on the runtime
806 <p><i>Inserting instructions</i></p>
809 There are essentially two ways to insert an <tt>Instruction</tt> into
810 an existing sequence of instructions that form a <tt>BasicBlock</tt>:
812 <li>Insertion into an explicit instruction list
814 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within
815 that <tt>BasicBlock</tt>, and a newly-created instruction
816 we wish to insert before <tt>*pi</tt>, we do the following:
819 BasicBlock* pb = ...;
820 Instruction* pi = ...;
821 Instruction* newInst = new Instruction(...);
822 pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb
826 <li>Insertion into an implicit instruction list
827 <p><tt>Instruction</tt> instances that are already in
828 <tt>BasicBlock</tt>s are implicitly associated with an existing
829 instruction list: the instruction list of the enclosing basic block.
830 Thus, we could have accomplished the same thing as the above code
831 without being given a <tt>BasicBlock</tt> by doing:
833 Instruction* pi = ...;
834 Instruction* newInst = new Instruction(...);
835 pi->getParent()->getInstList().insert(pi, newInst);
837 In fact, this sequence of steps occurs so frequently that the
838 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes
839 provide constructors which take (as a default parameter) a pointer to
840 an <tt>Instruction</tt> which the newly-created <tt>Instruction</tt>
841 should precede. That is, <tt>Instruction</tt> constructors are
842 capable of inserting the newly-created instance into the
843 <tt>BasicBlock</tt> of a provided instruction, immediately before that
844 instruction. Using an <tt>Instruction</tt> constructor with a
845 <tt>insertBefore</tt> (default) parameter, the above code becomes:
847 Instruction* pi = ...;
848 Instruction* newInst = new Instruction(..., pi);
850 which is much cleaner, especially if you're creating a lot of
851 instructions and adding them to <tt>BasicBlock</tt>s.
856 <!--_______________________________________________________________________-->
857 </ul><h4><a name="schanges_deleting"><hr size=0>Deleting
858 <tt>Instruction</tt>s</h4><ul>
860 Deleting an instruction from an existing sequence of instructions that form a <a
861 href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First, you
862 must have a pointer to the instruction that you wish to delete. Second, you
863 need to obtain the pointer to that instruction's basic block. You use the
864 pointer to the basic block to get its list of instructions and then use the
865 erase function to remove your instruction.<p>
870 <a href="#Instruction">Instruction</a> *I = .. ;
871 <a href="#BasicBlock">BasicBlock</a> *BB = I->getParent();
872 BB->getInstList().erase(I);
875 <!--_______________________________________________________________________-->
876 </ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
877 <tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
879 <p><i>Replacing individual instructions</i></p>
882 href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h
883 </a>" permits use of two very useful replace functions:
884 <tt>ReplaceInstWithValue</tt> and <tt>ReplaceInstWithInst</tt>.
888 <li><tt>ReplaceInstWithValue</tt>
890 <p>This function replaces all uses (within a basic block) of a given
891 instruction with a value, and then removes the original instruction.
892 The following example illustrates the replacement of the result of a
893 particular <tt>AllocaInst</tt> that allocates memory for a single
894 integer with an null pointer to an integer.</p>
897 AllocaInst* instToReplace = ...;
898 BasicBlock::iterator ii(instToReplace);
899 ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,
900 Constant::getNullValue(PointerType::get(Type::IntTy)));
903 <li><tt>ReplaceInstWithInst</tt>
905 <p>This function replaces a particular instruction with another
906 instruction. The following example illustrates the replacement of one
907 <tt>AllocaInst</tt> with another.<p>
910 AllocaInst* instToReplace = ...;
911 BasicBlock::iterator ii(instToReplace);
912 ReplaceInstWithInst(instToReplace->getParent()->getInstList(), ii,
913 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt");
917 <p><i>Replacing multiple uses of <tt>User</tt>s and
918 <tt>Value</tt>s</i></p>
920 You can use <tt>Value::replaceAllUsesWith</tt> and
921 <tt>User::replaceUsesOfWith</tt> to change more than one use at a
922 time. See the doxygen documentation for the <a
923 href="/doxygen/classValue.html">Value Class</a> and <a
924 href="/doxygen/classUser.html">User Class</a>, respectively, for more
927 <!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
928 include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
929 ReplaceInstWithValue, ReplaceInstWithInst
932 <!-- *********************************************************************** -->
933 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
934 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
935 <a name="coreclasses">The Core LLVM Class Hierarchy Reference
936 </b></font></td></tr></table><ul>
937 <!-- *********************************************************************** -->
939 The Core LLVM classes are the primary means of representing the program being
940 inspected or transformed. The core LLVM classes are defined in header files in
941 the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
945 <!-- ======================================================================= -->
946 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
947 <tr><td> </td><td width="100%">
948 <font color="#EEEEFF" face="Georgia,Palatino"><b>
949 <a name="Value">The <tt>Value</tt> class</a>
950 </b></font></td></tr></table><ul>
952 <tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
953 doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
956 The <tt>Value</tt> class is the most important class in LLVM Source base. It
957 represents a typed value that may be used (among other things) as an operand to
958 an instruction. There are many different types of <tt>Value</tt>s, such as <a
959 href="#Constant"><tt>Constant</tt></a>s, <a
960 href="#Argument"><tt>Argument</tt></a>s, and even <a
961 href="#Instruction"><tt>Instruction</tt></a>s and <a
962 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
964 A particular <tt>Value</tt> may be used many times in the LLVM representation
965 for a program. For example, an incoming argument to a function (represented
966 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
967 every instruction in the function that references the argument. To keep track
968 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
969 href="#User"><tt>User</tt></a>s that is using it (the <a
970 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
971 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
972 def-use information in the program, and is accessible through the <tt>use_</tt>*
973 methods, shown below.<p>
975 Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
976 this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
977 method. <a name="#nameWarning">In addition, all LLVM values can be named. The
978 "name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
981 %<b>foo</b> = add int 1, 2
984 The name of this instruction is "foo". <b>NOTE</b> that the name of any value
985 may be missing (an empty string), so names should <b>ONLY</b> be used for
986 debugging (making the source code easier to read, debugging printouts), they
987 should not be used to keep track of values or map between them. For this
988 purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
991 One important aspect of LLVM is that there is no distinction between an SSA
992 variable and the operation that produces it. Because of this, any reference to
993 the value produced by an instruction (or the value available as an incoming
994 argument, for example) is represented as a direct pointer to the class that
995 represents this value. Although this may take some getting used to, it
996 simplifies the representation and makes it easier to manipulate.<p>
999 <!-- _______________________________________________________________________ -->
1000 </ul><h4><a name="m_Value"><hr size=0>Important Public Members of
1001 the <tt>Value</tt> class</h4><ul>
1003 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
1004 <tt>Value::use_const_iterator</tt>
1005 - Typedef for const_iterator over the use-list<br>
1006 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
1007 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
1008 <tt>use_iterator use_begin()</tt>
1009 - Get an iterator to the start of the use-list.<br>
1010 <tt>use_iterator use_end()</tt>
1011 - Get an iterator to the end of the use-list.<br>
1012 <tt><a href="#User">User</a> *use_back()</tt>
1013 - Returns the last element in the list.<p>
1015 These 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>
1017 <li><tt><a href="#Type">Type</a> *getType() const</tt><p>
1018 This method returns the Type of the Value.
1020 <li><tt>bool hasName() const</tt><br>
1021 <tt>std::string getName() const</tt><br>
1022 <tt>void setName(const std::string &Name)</tt><p>
1024 This family of methods is used to access and assign a name to a <tt>Value</tt>,
1025 be aware of the <a href="#nameWarning">precaution above</a>.<p>
1028 <li><tt>void replaceAllUsesWith(Value *V)</tt><p>
1030 This method traverses the use list of a <tt>Value</tt> changing all <a
1031 href="#User"><tt>User</tt>s</a> of the current value to refer to "<tt>V</tt>"
1032 instead. For example, if you detect that an instruction always produces a
1033 constant value (for example through constant folding), you can replace all uses
1034 of the instruction with the constant like this:<p>
1037 Inst->replaceAllUsesWith(ConstVal);
1042 <!-- ======================================================================= -->
1043 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1044 <tr><td> </td><td width="100%">
1045 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1046 <a name="User">The <tt>User</tt> class</a>
1047 </b></font></td></tr></table><ul>
1049 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
1050 doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
1051 Superclass: <a href="#Value"><tt>Value</tt></a><p>
1054 The <tt>User</tt> class is the common base class of all LLVM nodes that may
1055 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1056 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1057 referring to. The <tt>User</tt> class itself is a subclass of
1060 The operands of a <tt>User</tt> point directly to the LLVM <a
1061 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1062 Single Assignment (SSA) form, there can only be one definition referred to,
1063 allowing this direct connection. This connection provides the use-def
1064 information in LLVM.<p>
1066 <!-- _______________________________________________________________________ -->
1067 </ul><h4><a name="m_User"><hr size=0>Important Public Members of
1068 the <tt>User</tt> class</h4><ul>
1070 The <tt>User</tt> class exposes the operand list in two ways: through an index
1071 access interface and through an iterator based interface.<p>
1073 <li><tt>Value *getOperand(unsigned i)</tt><br>
1074 <tt>unsigned getNumOperands()</tt><p>
1076 These two methods expose the operands of the <tt>User</tt> in a convenient form
1077 for direct access.<p>
1079 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
1080 <tt>User::op_const_iterator</tt>
1081 <tt>use_iterator op_begin()</tt>
1082 - Get an iterator to the start of the operand list.<br>
1083 <tt>use_iterator op_end()</tt>
1084 - Get an iterator to the end of the operand list.<p>
1086 Together, these methods make up the iterator based interface to the operands of
1091 <!-- ======================================================================= -->
1092 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1093 <tr><td> </td><td width="100%">
1094 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1095 <a name="Instruction">The <tt>Instruction</tt> class</a>
1096 </b></font></td></tr></table><ul>
1099 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
1100 doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
1101 Superclasses: <a href="#User"><tt>User</tt></a>, <a
1102 href="#Value"><tt>Value</tt></a><p>
1104 The <tt>Instruction</tt> class is the common base class for all LLVM
1105 instructions. It provides only a few methods, but is a very commonly used
1106 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1107 opcode (instruction type) and the parent <a
1108 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1109 into. To represent a specific type of instruction, one of many subclasses of
1110 <tt>Instruction</tt> are used.<p>
1112 Because the <tt>Instruction</tt> class subclasses the <a
1113 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1114 way as for other <a href="#User"><tt>User</tt></a>s (with the
1115 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1116 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
1118 An important file for the <tt>Instruction</tt> class is the
1119 <tt>llvm/Instruction.def</tt> file. This file contains some meta-data about the
1120 various different types of instructions in LLVM. It describes the enum values
1121 that are used as opcodes (for example <tt>Instruction::Add</tt> and
1122 <tt>Instruction::SetLE</tt>), as well as the concrete sub-classes of
1123 <tt>Instruction</tt> that implement the instruction (for example <tt><a
1124 href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1125 href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1126 this file confused doxygen, so these enum values don't show up correctly in the
1127 <a href="/doxygen/classInstruction.html">doxygen output</a>.<p>
1130 <!-- _______________________________________________________________________ -->
1131 </ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
1132 the <tt>Instruction</tt> class</h4><ul>
1134 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
1136 Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
1137 <tt>Instruction</tt> is embedded into.<p>
1139 <li><tt>bool hasSideEffects()</tt><p>
1141 Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
1142 <tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
1144 <li><tt>unsigned getOpcode()</tt><p>
1146 Returns the opcode for the <tt>Instruction</tt>.<p>
1148 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt><p>
1150 Returns another instance of the specified instruction, identical in all ways to
1151 the original except that the instruction has no parent (ie it's not embedded
1152 into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>), and it has no name.<p>
1158 \subsection{Subclasses of Instruction :}
1160 <li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
1162 <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.
1164 <li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
1166 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
1167 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
1168 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
1171 <li>PHINode : This represents the PHI instructions in the SSA form.
1173 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
1174 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
1175 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
1176 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
1177 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
1178 Add an incoming value to the end of the PHI list
1179 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
1180 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
1182 <li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
1183 <li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
1185 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
1187 <li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
1189 <li><tt>Value * getPointerOperand()</tt>: Returns the Pointer Operand which is typically the 0th operand.
1191 <li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
1193 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
1194 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
1195 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
1203 <!-- ======================================================================= -->
1204 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1205 <tr><td> </td><td width="100%">
1206 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1207 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1208 </b></font></td></tr></table><ul>
1211 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
1212 doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
1213 Superclass: <a href="#Value"><tt>Value</tt></a><p>
1216 This class represents a single entry multiple exit section of the code, commonly
1217 known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
1218 maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
1219 the body of the block. Matching the language definition, the last element of
1220 this list of instructions is always a terminator instruction (a subclass of the
1221 <a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
1223 In addition to tracking the list of instructions that make up the block, the
1224 <tt>BasicBlock</tt> class also keeps track of the <a
1225 href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
1227 Note that <tt>BasicBlock</tt>s themselves are <a
1228 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1229 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1233 <!-- _______________________________________________________________________ -->
1234 </ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
1235 the <tt>BasicBlock</tt> class</h4><ul>
1237 <li><tt>BasicBlock(const std::string &Name = "", <a
1238 href="#Function">Function</a> *Parent = 0)</tt><p>
1240 The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1241 insertion into a function. The constructor simply takes a name for the new
1242 block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
1243 into. If the <tt>Parent</tt> parameter is specified, the new
1244 <tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
1245 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1246 manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
1248 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1249 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1250 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1251 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1253 These methods and typedefs are forwarding functions that have the same semantics
1254 as the standard library methods of the same names. These methods expose the
1255 underlying instruction list of a basic block in a way that is easy to
1256 manipulate. To get the full complement of container operations (including
1257 operations to update the list), you must use the <tt>getInstList()</tt>
1260 <li><tt>BasicBlock::InstListType &getInstList()</tt><p>
1262 This method is used to get access to the underlying container that actually
1263 holds the Instructions. This method must be used when there isn't a forwarding
1264 function in the <tt>BasicBlock</tt> class for the operation that you would like
1265 to perform. Because there are no forwarding functions for "updating"
1266 operations, you need to use this if you want to update the contents of a
1267 <tt>BasicBlock</tt>.<p>
1269 <li><tt><A href="#Function">Function</a> *getParent()</tt><p>
1271 Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1272 embedded into, or a null pointer if it is homeless.<p>
1274 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
1276 Returns a pointer to the terminator instruction that appears at the end of the
1277 <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1278 instruction in the block is not a terminator, then a null pointer is
1282 <!-- ======================================================================= -->
1283 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1284 <tr><td> </td><td width="100%">
1285 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1286 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1287 </b></font></td></tr></table><ul>
1290 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
1291 doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
1292 Superclasses: <a href="#User"><tt>User</tt></a>, <a
1293 href="#Value"><tt>Value</tt></a><p>
1295 Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1296 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1297 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1298 Because they are visible at global scope, they are also subject to linking with
1299 other globals defined in different translation units. To control the linking
1300 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1301 <tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
1303 If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1304 <tt>static</tt> in C), it is not visible to code outside the current translation
1305 unit, and does not participate in linking. If it has external linkage, it is
1306 visible to external code, and does participate in linking. In addition to
1307 linkage information, <tt>GlobalValue</tt>s keep track of which <a
1308 href="#Module"><tt>Module</tt></a> they are currently part of.<p>
1310 Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
1311 their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
1312 always a pointer to its contents. This is explained in the LLVM Language
1313 Reference Manual.<p>
1316 <!-- _______________________________________________________________________ -->
1317 </ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
1318 the <tt>GlobalValue</tt> class</h4><ul>
1320 <li><tt>bool hasInternalLinkage() const</tt><br>
1321 <tt>bool hasExternalLinkage() const</tt><br>
1322 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
1324 These methods manipulate the linkage characteristics of the
1325 <tt>GlobalValue</tt>.<p>
1327 <li><tt><a href="#Module">Module</a> *getParent()</tt><p>
1329 This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
1330 currently embedded into.<p>
1334 <!-- ======================================================================= -->
1335 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1336 <tr><td> </td><td width="100%">
1337 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1338 <a name="Function">The <tt>Function</tt> class</a>
1339 </b></font></td></tr></table><ul>
1342 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
1343 doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
1344 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1345 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1347 The <tt>Function</tt> class represents a single procedure in LLVM. It is
1348 actually one of the more complex classes in the LLVM heirarchy because it must
1349 keep track of a large amount of data. The <tt>Function</tt> class keeps track
1350 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
1351 href="#Argument"><tt>Argument</tt></a>s, and a <a
1352 href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
1354 The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
1355 used part of <tt>Function</tt> objects. The list imposes an implicit ordering
1356 of the blocks in the function, which indicate how the code will be layed out by
1357 the backend. Additionally, the first <a
1358 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1359 <tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
1360 block. There are no implicit exit nodes, and in fact there may be multiple exit
1361 nodes from a single <tt>Function</tt>. If the <a
1362 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1363 the <tt>Function</tt> is actually a function declaration: the actual body of the
1364 function hasn't been linked in yet.<p>
1366 In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1367 <tt>Function</tt> class also keeps track of the list of formal <a
1368 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1369 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1370 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1371 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
1373 The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
1374 feature that is only used when you have to look up a value by name. Aside from
1375 that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
1376 make sure that there are not conflicts between the names of <a
1377 href="#Instruction"><tt>Instruction</tt></a>s, <a
1378 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1379 href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
1382 <!-- _______________________________________________________________________ -->
1383 </ul><h4><a name="m_Function"><hr size=0>Important Public Members of
1384 the <tt>Function</tt> class</h4><ul>
1386 <li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
1388 Constructor used when you need to create new <tt>Function</tt>s to add the the
1389 program. The constructor must specify the type of the function to create and
1390 whether or not it should start out with internal or external linkage.<p>
1392 <li><tt>bool isExternal()</tt><p>
1394 Return whether or not the <tt>Function</tt> has a body defined. If the function
1395 is "external", it does not have a body, and thus must be resolved by linking
1396 with a function defined in a different translation unit.<p>
1399 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
1400 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
1401 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1402 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1404 These are forwarding methods that make it easy to access the contents of a
1405 <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1408 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
1410 Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
1411 neccesary to use when you need to update the list or perform a complex action
1412 that doesn't have a forwarding method.<p>
1415 <li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
1416 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
1417 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
1418 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
1420 These are forwarding methods that make it easy to access the contents of a
1421 <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
1423 <li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
1425 Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1426 neccesary to use when you need to update the list or perform a complex action
1427 that doesn't have a forwarding method.<p>
1431 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
1433 Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1434 function. Because the entry block for the function is always the first block,
1435 this returns the first block of the <tt>Function</tt>.<p>
1437 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1438 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
1440 This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
1441 and returns the return type of the function, or the <a
1442 href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
1444 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1446 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1447 <tt>Function</tt>.<p>
1451 <!-- ======================================================================= -->
1452 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1453 <tr><td> </td><td width="100%">
1454 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1455 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1456 </b></font></td></tr></table><ul>
1459 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
1460 doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
1461 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1462 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1464 Global variables are represented with the (suprise suprise)
1465 <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
1466 also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
1467 are always referenced by their address (global values must live in memory, so
1468 their "name" refers to their address). Global variables may have an initial
1469 value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
1470 have an initializer, they may be marked as "constant" themselves (indicating
1471 that their contents never change at runtime).<p>
1474 <!-- _______________________________________________________________________ -->
1475 </ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
1476 <tt>GlobalVariable</tt> class</h4><ul>
1478 <li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
1479 isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
1480 &Name = "")</tt><p>
1482 Create a new global variable of the specified type. If <tt>isConstant</tt> is
1483 true then the global variable will be marked as unchanging for the program, and
1484 if <tt>isInternal</tt> is true the resultant global variable will have internal
1485 linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
1488 <li><tt>bool isConstant() const</tt><p>
1490 Returns true if this is a global variable is known not to be modified at
1494 <li><tt>bool hasInitializer()</tt><p>
1496 Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
1499 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
1501 Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
1502 this method if there is no initializer.<p>
1505 <!-- ======================================================================= -->
1506 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1507 <tr><td> </td><td width="100%">
1508 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1509 <a name="Module">The <tt>Module</tt> class</a>
1510 </b></font></td></tr></table><ul>
1513 href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
1514 doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
1516 The <tt>Module</tt> class represents the top level structure present in LLVM
1517 programs. An LLVM module is effectively either a translation unit of the
1518 original program or a combination of several translation units merged by the
1519 linker. The <tt>Module</tt> class keeps track of a list of <a
1520 href="#Function"><tt>Function</tt></a>s, a list of <a
1521 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1522 href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1523 helpful member functions that try to make common operations easy.<p>
1526 <!-- _______________________________________________________________________ -->
1527 </ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
1528 <tt>Module</tt> class</h4><ul>
1530 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
1531 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
1532 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1533 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1535 These are forwarding methods that make it easy to access the contents of a
1536 <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1539 <li><tt>Module::FunctionListType &getFunctionList()</tt><p>
1541 Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1542 neccesary to use when you need to update the list or perform a complex action
1543 that doesn't have a forwarding method.<p>
1545 <!-- Global Variable -->
1548 <li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
1549 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
1550 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
1551 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
1553 These are forwarding methods that make it easy to access the contents of a
1554 <tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
1557 <li><tt>Module::GlobalListType &getGlobalList()</tt><p>
1559 Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
1560 This is neccesary to use when you need to update the list or perform a complex
1561 action that doesn't have a forwarding method.<p>
1564 <!-- Symbol table stuff -->
1567 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1569 Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for
1570 this <tt>Module</tt>.<p>
1573 <!-- Convenience methods -->
1576 <li><tt><a href="#Function">Function</a> *getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
1578 Look up the specified function in the <tt>Module</tt> <a
1579 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
1583 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
1584 &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
1586 Look up the specified function in the <tt>Module</tt> <a
1587 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
1588 external declaration for the function and return it.<p>
1591 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
1593 If there is at least one entry in the <a
1594 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
1595 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
1599 <li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
1602 Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
1603 <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
1604 is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
1608 <!-- ======================================================================= -->
1609 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1610 <tr><td> </td><td width="100%">
1611 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1612 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
1613 </b></font></td></tr></table><ul>
1615 Constant represents a base class for different types of constants. It is
1616 subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
1617 ConstantArray etc for representing the various types of Constants.<p>
1620 <!-- _______________________________________________________________________ -->
1621 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1623 <li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
1627 Important Subclasses of Constant<p>
1630 <li>ConstantSInt : This subclass of Constant represents a signed integer constant.
1632 <li><tt>int64_t getValue() const</tt>: Returns the underlying value of this constant.
1634 <li>ConstantUInt : This class represents an unsigned integer.
1636 <li><tt>uint64_t getValue() const</tt>: Returns the underlying value of this constant.
1638 <li>ConstantFP : This class represents a floating point constant.
1640 <li><tt>double getValue() const</tt>: Returns the underlying value of this constant.
1642 <li>ConstantBool : This represents a boolean constant.
1644 <li><tt>bool getValue() const</tt>: Returns the underlying value of this constant.
1646 <li>ConstantArray : This represents a constant array.
1648 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1650 <li>ConstantStruct : This represents a constant struct.
1652 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1654 <li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
1656 <li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
1661 <!-- ======================================================================= -->
1662 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1663 <tr><td> </td><td width="100%">
1664 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1665 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
1666 </b></font></td></tr></table><ul>
1668 Type as noted earlier is also a subclass of a Value class. Any primitive
1669 type (like int, short etc) in LLVM is an instance of Type Class. All
1670 other types are instances of subclasses of type like FunctionType,
1671 ArrayType etc. DerivedType is the interface for all such dervied types
1672 including FunctionType, ArrayType, PointerType, StructType. Types can have
1673 names. They can be recursive (StructType). There exists exactly one instance
1674 of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
1676 <!-- _______________________________________________________________________ -->
1677 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1679 <li><tt>PrimitiveID getPrimitiveID() const</tt>: Returns the base type of the type.
1680 <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.
1681 <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.
1682 <li><tt> bool isInteger() const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
1683 <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.
1685 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two floating point types.
1686 <li><tt>bool isRecursive() const</tt>: Returns rue if the type graph contains a cycle.
1687 <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.
1688 <li><tt>bool isPrimitiveType() const</tt>: Returns true if it is a primitive type.
1689 <li><tt>bool isDerivedType() const</tt>: Returns true if it is a derived type.
1690 <li><tt>const Type * getContainedType (unsigned i) const</tt>:
1691 This 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.
1692 <li><tt>unsigned getNumContainedTypes() const</tt>: Return the number of types in the derived type.
1700 <li>SequentialType : This is subclassed by ArrayType and PointerType
1702 <li><tt>const Type * getElementType() const</tt>: Returns the type of each of the elements in the sequential type.
1704 <li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
1706 <li><tt>unsigned getNumElements() const</tt>: Returns the number of elements in the array.
1708 <li>PointerType : Subclass of SequentialType for pointer types.
1709 <li>StructType : subclass of DerivedTypes for struct types
1710 <li>FunctionType : subclass of DerivedTypes for function types.
1714 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg function
1715 <li><tt> const Type * getReturnType() const</tt>: Returns the return type of the function.
1716 <li><tt> const ParamTypes &getParamTypes() const</tt>: Returns a vector of parameter types.
1717 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
1718 <li><tt> const unsigned getNumParams() const</tt>: Returns the number of formal parameters.
1725 <!-- ======================================================================= -->
1726 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1727 <tr><td> </td><td width="100%">
1728 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1729 <a name="Argument">The <tt>Argument</tt> class</a>
1730 </b></font></td></tr></table><ul>
1732 This subclass of Value defines the interface for incoming formal arguments to a
1733 function. A Function maitanis a list of its formal arguments. An argument has a
1734 pointer to the parent Function.
1739 <!-- *********************************************************************** -->
1741 <!-- *********************************************************************** -->
1744 <address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
1745 <a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
1746 <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
1747 <!-- hhmts start -->
1748 Last modified: Wed Nov 20 12:21:34 CST 2002
1750 </font></body></html>