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6 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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.<br>
168 <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
171 <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
173 href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
176 <li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
181 You are also encouraged to take a look at the <a
182 href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
183 to write maintainable code more than where to put your curly braces.<p>
186 <!-- *********************************************************************** -->
187 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
188 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
189 <a name="apis">Important and useful LLVM APIs
190 </b></font></td></tr></table><ul>
191 <!-- *********************************************************************** -->
193 Here we highlight some LLVM APIs that are generally useful and good to know
194 about when writing transformations.<p>
196 <!-- ======================================================================= -->
197 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
198 <tr><td> </td><td width="100%">
199 <font color="#EEEEFF" face="Georgia,Palatino"><b>
200 <a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
201 </b></font></td></tr></table><ul>
203 The LLVM source-base makes extensive use of a custom form of RTTI. These
204 templates have many similarities to the C++ <tt>dynamic_cast<></tt>
205 operator, but they don't have some drawbacks (primarily stemming from the fact
206 that <tt>dynamic_cast<></tt> only works on classes that have a v-table).
207 Because they are used so often, you must know what they do and how they work.
208 All of these templates are defined in the <a
209 href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a> file (note
210 that you very rarely have to include this file directly).<p>
214 <dt><tt>isa<></tt>:
216 <dd>The <tt>isa<></tt> operator works exactly like the Java
217 "<tt>instanceof</tt>" operator. It returns true or false depending on whether a
218 reference or pointer points to an instance of the specified class. This can be
219 very useful for constraint checking of various sorts (example below).<p>
222 <dt><tt>cast<></tt>:
224 <dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
225 converts a pointer or reference from a base class to a derived cast, causing an
226 assertion failure if it is not really an instance of the right type. This
227 should be used in cases where you have some information that makes you believe
228 that something is of the right type. An example of the <tt>isa<></tt> and
229 <tt>cast<></tt> template is:<p>
232 static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
233 if (isa<<a href="#Constant">Constant</a>>(V) || isa<<a href="#Argument">Argument</a>>(V) || isa<<a href="#GlobalValue">GlobalValue</a>>(V))
236 <i>// Otherwise, it must be an instruction...</i>
237 return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
240 Note that you should <b>not</b> use an <tt>isa<></tt> test followed by a
241 <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt> operator.<p>
244 <dt><tt>dyn_cast<></tt>:
246 <dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
247 checks to see if the operand is of the specified type, and if so, returns a
248 pointer to it (this operator does not work with references). If the operand is
249 not of the correct type, a null pointer is returned. Thus, this works very much
250 like the <tt>dynamic_cast</tt> operator in C++, and should be used in the same
251 circumstances. Typically, the <tt>dyn_cast<></tt> operator is used in an
252 <tt>if</tt> statement or some other flow control statement like this:<p>
255 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
260 This form of the <tt>if</tt> statement effectively combines together a call to
261 <tt>isa<></tt> and a call to <tt>cast<></tt> into one statement,
262 which is very convenient.<p>
264 Another common example is:<p>
267 <i>// Loop over all of the phi nodes in a basic block</i>
268 BasicBlock::iterator BBI = BB->begin();
269 for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(&*BBI); ++BBI)
273 Note that the <tt>dyn_cast<></tt> operator, like C++'s
274 <tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused. In
275 particular you should not use big chained <tt>if/then/else</tt> blocks to check
276 for lots of different variants of classes. If you find yourself wanting to do
277 this, it is much cleaner and more efficient to use the InstVisitor class to
278 dispatch over the instruction type directly.<p>
281 <dt><tt>cast_or_null<></tt>:
283 <dd>The <tt>cast_or_null<></tt> operator works just like the
284 <tt>cast<></tt> operator, except that it allows for a null pointer as an
285 argument (which it then propagates). This can sometimes be useful, allowing you
286 to combine several null checks into one.<p>
289 <dt><tt>dyn_cast_or_null<></tt>:
291 <dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
292 <tt>dyn_cast<></tt> operator, except that it allows for a null pointer as
293 an argument (which it then propagates). This can sometimes be useful, allowing
294 you to combine several null checks into one.<p>
298 These five templates can be used with any classes, whether they have a v-table
299 or not. To add support for these templates, you simply need to add
300 <tt>classof</tt> static methods to the class you are interested casting to.
301 Describing this is currently outside the scope of this document, but there are
302 lots of examples in the LLVM source base.<p>
305 <!-- ======================================================================= -->
306 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
307 <tr><td> </td><td width="100%">
308 <font color="#EEEEFF" face="Georgia,Palatino"><b>
309 <a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
310 </b></font></td></tr></table><ul>
312 Often when working on your pass you will put a bunch of debugging printouts and
313 other code into your pass. After you get it working, you want to remove
314 it... but you may need it again in the future (to work out new bugs that you run
317 Naturally, because of this, you don't want to delete the debug printouts, but
318 you don't want them to always be noisy. A standard compromise is to comment
319 them out, allowing you to enable them if you need them in the future.<p>
322 href="/doxygen/StatisticReporter_8h-source.html">StatisticReporter.h</a></tt>"
323 file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
324 this problem. Basically, you can put arbitrary code into the argument of the
325 <tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' is run with the
326 '<tt>-debug</tt>' command line argument:
330 DEBUG(std::cerr << "I am here!\n");
334 Then you can run your pass like this:<p>
337 $ opt < a.bc > /dev/null -mypass
339 $ opt < a.bc > /dev/null -mypass -debug
344 Using the <tt>DEBUG()</tt> macro instead of a home brewed solution allows you to
345 now have to create "yet another" command line option for the debug output for
346 your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized
347 builds, so they do not cause a performance impact at all.<p>
350 <!-- ======================================================================= -->
351 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
352 <tr><td> </td><td width="100%">
353 <font color="#EEEEFF" face="Georgia,Palatino"><b>
354 <a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
356 </b></font></td></tr></table><ul>
359 href="/doxygen/StatisticReporter_8h-source.html">StatisticReporter.h</a></tt>"
360 file provides a template named <tt>Statistic</tt> that is used as a unified way
361 to keeping track of what the LLVM compiler is doing and how effective various
362 optimizations are. It is useful to see what optimizations are contributing to
363 making a particular program run faster.<p>
365 Often you may run your pass on some big program, and you're interested to see
366 how many times it makes a certain transformation. Although you can do this with
367 hand inspection, or some ad-hoc method, this is a real pain and not very useful
368 for big programs. Using the <tt>Statistic</tt> template makes it very easy to
369 keep track of this information, and the calculated information is presented in a
370 uniform manner with the rest of the passes being executed.<p>
372 There are many examples of <tt>Statistic</tt> users, but this basics of using it
376 <li>Define your statistic like this:<p>
379 static Statistic<> NumXForms("mypassname\t- The # of times I did stuff");
382 The <tt>Statistic</tt> template can emulate just about any data-type, but if you
383 do not specify a template argument, it defaults to acting like an unsigned int
384 counter (this is usually what you want).<p>
386 <li>Whenever you make a transformation, bump the counter:<p>
389 ++NumXForms; // I did stuff
394 That's all you have to do. To get '<tt>opt</tt>' to print out the statistics
395 gathered, use the '<tt>-stats</tt>' option:<p>
398 $ opt -stats -mypassname < program.bc > /dev/null
399 ... statistic output ...
402 When running <tt>gccas</tt> on a C file from the SPEC benchmark suite, it gives
403 a report that looks like this:<p>
406 7646 bytecodewriter - Number of normal instructions
407 725 bytecodewriter - Number of oversized instructions
408 129996 bytecodewriter - Number of bytecode bytes written
409 2817 raise - Number of insts DCEd or constprop'd
410 3213 raise - Number of cast-of-self removed
411 5046 raise - Number of expression trees converted
412 75 raise - Number of other getelementptr's formed
413 138 raise - Number of load/store peepholes
414 42 deadtypeelim - Number of unused typenames removed from symtab
415 392 funcresolve - Number of varargs functions resolved
416 27 globaldce - Number of global variables removed
417 2 adce - Number of basic blocks removed
418 134 cee - Number of branches revectored
419 49 cee - Number of setcc instruction eliminated
420 532 gcse - Number of loads removed
421 2919 gcse - Number of instructions removed
422 86 indvars - Number of cannonical indvars added
423 87 indvars - Number of aux indvars removed
424 25 instcombine - Number of dead inst eliminate
425 434 instcombine - Number of insts combined
426 248 licm - Number of load insts hoisted
427 1298 licm - Number of insts hoisted to a loop pre-header
428 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
429 75 mem2reg - Number of alloca's promoted
430 1444 cfgsimplify - Number of blocks simplified
433 Obviously, with so many optimizations, having a unified framework for this stuff
434 is very nice. Making your pass fit well into the framework makes it more
435 maintainable and useful.<p>
438 <!-- *********************************************************************** -->
439 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
440 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
441 <a name="common">Helpful Hints for Common Operations
442 </b></font></td></tr></table><ul> <!--
443 *********************************************************************** -->
445 This section describes how to perform some very simple transformations of LLVM
446 code. This is meant to give examples of common idioms used, showing the
447 practical side of LLVM transformations.<p>
449 Because this is a "how-to" section, you should also read about the main classes
450 that you will be working with. The <a href="#coreclasses">Core LLVM Class
451 Hierarchy Reference</a> contains details and descriptions of the main classes
452 that you should know about.<p>
454 <!-- NOTE: this section should be heavy on example code -->
457 <!-- ======================================================================= -->
458 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
459 <tr><td> </td><td width="100%">
460 <font color="#EEEEFF" face="Georgia,Palatino"><b>
461 <a name="inspection">Basic Inspection and Traversal Routines</a>
462 </b></font></td></tr></table><ul>
464 The LLVM compiler infrastructure have many different data structures that may be
465 traversed. Following the example of the C++ standard template library, the
466 techniques used to traverse these various data structures are all basically the
467 same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
468 method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
469 function returns an iterator pointing to one past the last valid element of the
470 sequence, and there is some <tt>XXXiterator</tt> data type that is common
471 between the two operations.<p>
473 Because the pattern for iteration is common across many different aspects of the
474 program representation, the standard template library algorithms may be used on
475 them, and it is easier to remember how to iterate. First we show a few common
476 examples of the data structures that need to be traversed. Other data
477 structures are traversed in very similar ways.<p>
480 <!-- _______________________________________________________________________ -->
481 </ul><h4><a name="iterate_function"><hr size=0>Iterating over the <a
482 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
483 href="#Function"><tt>Function</tt></a> </h4><ul>
485 It's quite common to have a <tt>Function</tt> instance that you'd like
486 to transform in some way; in particular, you'd like to manipulate its
487 <tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over
488 all of the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>.
489 The following is an example that prints the name of a
490 <tt>BasicBlock</tt> and the number of <tt>Instruction</tt>s it
494 // func is a pointer to a Function instance
495 for(Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {
497 // print out the name of the basic block if it has one, and then the
498 // number of instructions that it contains
500 cerr << "Basic block (name=" << i->getName() << ") has "
501 << i->size() << " instructions.\n";
505 Note that i can be used as if it were a pointer for the purposes of
506 invoking member functions of the <tt>Instruction</tt> class. This is
507 because the indirection operator is overloaded for the iterator
508 classes. In the above code, the expression <tt>i->size()</tt> is
509 exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.
511 <!-- _______________________________________________________________________ -->
512 </ul><h4><a name="iterate_basicblock"><hr size=0>Iterating over the <a
513 href="#Instruction"><tt>Instruction</tt></a>s in a <a
514 href="#BasicBlock"><tt>BasicBlock</tt></a> </h4><ul>
516 Just like when dealing with <tt>BasicBlock</tt>s in
517 <tt>Function</tt>s, it's easy to iterate over the individual
518 instructions that make up <tt>BasicBlock</tt>s. Here's a code snippet
519 that prints out each instruction in a <tt>BasicBlock</tt>:
522 // blk is a pointer to a BasicBlock instance
523 for(BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
524 // the next statement works since operator<<(ostream&,...)
525 // is overloaded for Instruction&
526 cerr << *i << "\n";
529 However, this isn't really the best way to print out the contents of a
530 <tt>BasicBlock</tt>! Since the ostream operators are overloaded for
531 virtually anything you'll care about, you could have just invoked the
532 print routine on the basic block itself: <tt>cerr << *blk <<
535 Note that currently operator<< is implemented for <tt>Value*</tt>, so it
536 will print out the contents of the pointer, instead of
537 the pointer value you might expect. This is a deprecated interface that will
538 be removed in the future, so it's best not to depend on it. To print out the
539 pointer value for now, you must cast to <tt>void*</tt>.<p>
542 <!-- _______________________________________________________________________ -->
543 </ul><h4><a name="iterate_institer"><hr size=0>Iterating over the <a
544 href="#Instruction"><tt>Instruction</tt></a>s in a <a
545 href="#Function"><tt>Function</tt></a></h4><ul>
547 If you're finding that you commonly iterate over a <tt>Function</tt>'s
548 <tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s
549 <tt>Instruction</tt>s, <tt>InstIterator</tt> should be used instead.
550 You'll need to include <a href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>, and then
551 instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
552 small example that shows how to dump all instructions in a function to
553 stderr (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
554 <tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&</tt>!):
557 #include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
559 // Suppose F is a ptr to a function
560 for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
561 cerr << **i << "\n";
564 Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
565 worklist with its initial contents. For example, if you wanted to
566 initialize a worklist to contain all instructions in a
567 <tt>Function</tt> F, all you would need to do is something like:
570 std::set<Instruction*> worklist;
571 worklist.insert(inst_begin(F), inst_end(F));
574 The STL set <tt>worklist</tt> would now contain all instructions in
575 the <tt>Function</tt> pointed to by F.
577 <!-- _______________________________________________________________________ -->
578 </ul><h4><a name="iterate_convert"><hr size=0>Turning an iterator into a class
579 pointer (and vice-versa) </h4><ul>
581 Sometimes, it'll be useful to grab a reference (or pointer) to a class
582 instance when all you've got at hand is an iterator. Well, extracting
583 a reference or a pointer from an iterator is very straightforward.
584 Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and
585 <tt>j</tt> is a <tt>BasicBlock::const_iterator</tt>:
588 Instruction& inst = *i; // grab reference to instruction reference
589 Instruction* pinst = &*i; // grab pointer to instruction reference
590 const Instruction& inst = *j;
592 However, the iterators you'll be working with in the LLVM framework
593 are special: they will automatically convert to a ptr-to-instance type
594 whenever they need to. Instead of dereferencing the iterator and then
595 taking the address of the result, you can simply assign the iterator
596 to the proper pointer type and you get the dereference and address-of
597 operation as a result of the assignment (behind the scenes, this is a
598 result of overloading casting mechanisms). Thus the last line of the
601 <pre>Instruction* pinst = &*i;</pre>
603 is semantically equivalent to
605 <pre>Instruction* pinst = i;</pre>
607 <b>Caveat emptor</b>: The above syntax works <i>only</i> when you're <i>not</i>
608 working with <tt>dyn_cast</tt>. The template definition of <tt><a
609 href="#isa">dyn_cast</a></tt> isn't implemented to handle this yet, so you'll
610 still need the following in order for things to work properly:
613 BasicBlock::iterator bbi = ...;
614 <a href="#BranchInst">BranchInst</a>* b = <a href="#isa">dyn_cast</a><<a href="#BranchInst">BranchInst</a>>(&*bbi);
617 It's also possible to turn a class pointer into the corresponding
618 iterator. Usually, this conversion is quite inexpensive. The
619 following code snippet illustrates use of the conversion constructors
620 provided by LLVM iterators. By using these, you can explicitly grab
621 the iterator of something without actually obtaining it via iteration
625 void printNextInstruction(Instruction* inst) {
626 BasicBlock::iterator it(inst);
627 ++it; // after this line, it refers to the instruction after *inst.
628 if(it != inst->getParent()->end()) cerr << *it << "\n";
631 Of course, this example is strictly pedagogical, because it'd be much
632 better to explicitly grab the next instruction directly from inst.
635 <!--_______________________________________________________________________-->
636 </ul><h4><a name="iterate_complex"><hr size=0>Finding call sites: a slightly
637 more complex example </h4><ul>
639 Say that you're writing a FunctionPass and would like to count all the
640 locations in the entire module (that is, across every
641 <tt>Function</tt>) where a certain function (i.e. some
642 <tt>Function</tt>*) already in scope. As you'll learn later, you may
643 want to use an <tt>InstVisitor</tt> to accomplish this in a much more
644 straightforward manner, but this example will allow us to explore how
645 you'd do it if you didn't have <tt>InstVisitor</tt> around. In
646 pseudocode, this is what we want to do:
649 initialize callCounter to zero
650 for each Function f in the Module
651 for each BasicBlock b in f
652 for each Instruction i in b
653 if(i is a CallInst and calls the given function)
654 increment callCounter
657 And the actual code is (remember, since we're writing a
658 <tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply
659 has to override the <tt>runOnFunction</tt> method...):
662 Function* targetFunc = ...;
664 class OurFunctionPass : public FunctionPass {
666 OurFunctionPass(): callCounter(0) { }
668 virtual runOnFunction(Function& F) {
669 for(Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
670 for(BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {
671 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a href="#CallInst">CallInst</a>>(&*i)) {
672 // we know we've encountered a call instruction, so we
673 // need to determine if it's a call to the
674 // function pointed to by m_func or not.
676 if(callInst->getCalledFunction() == targetFunc)
683 unsigned callCounter;
687 <!--_______________________________________________________________________-->
688 </ul><h4><a name="iterate_chains"><hr size=0>Iterating over def-use &
689 use-def chains</h4><ul>
691 Frequently, we might have an instance of the <a
692 href="/doxygen/classValue.html">Value Class</a> and we want to
693 determine which <tt>User</tt>s use the <tt>Value</tt>. The list of
694 all <tt>User</tt>s of a particular <tt>Value</tt> is called a
695 <i>def-use</i> chain. For example, let's say we have a
696 <tt>Function*</tt> named <tt>F</tt> to a particular function
697 <tt>foo</tt>. Finding all of the instructions that <i>use</i>
698 <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain of
704 for(Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {
705 if(Instruction* Inst = dyn_cast<Instruction>(*i)) {
706 cerr << "F is used in instruction:\n";
707 cerr << *Inst << "\n";
712 Alternately, it's common to have an instance of the <a
713 href="/doxygen/classUser.html">User Class</a> and need to know what
714 <tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used
715 by a <tt>User</tt> is known as a <i>use-def</i> chain. Instances of
716 class <tt>Instruction</tt> are common <tt>User</tt>s, so we might want
717 to iterate over all of the values that a particular instruction uses
718 (that is, the operands of the particular <tt>Instruction</tt>):
721 Instruction* pi = ...;
723 for(User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {
731 def-use chains ("finding all users of"): Value::use_begin/use_end
732 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
735 <!-- ======================================================================= -->
736 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
737 <tr><td> </td><td width="100%">
738 <font color="#EEEEFF" face="Georgia,Palatino"><b>
739 <a name="simplechanges">Making simple changes</a>
740 </b></font></td></tr></table><ul>
742 There are some primitive transformation operations present in the LLVM
743 infrastructure that are worth knowing about. When performing
744 transformations, it's fairly common to manipulate the contents of
745 basic blocks. This section describes some of the common methods for
746 doing so and gives example code.
748 <!--_______________________________________________________________________-->
749 </ul><h4><a name="schanges_creating"><hr size=0>Creating and inserting
750 new <tt>Instruction</tt>s</h4><ul>
752 <i>Instantiating Instructions</i>
754 <p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
755 constructor for the kind of instruction to instantiate and provide the
756 necessary parameters. For example, an <tt>AllocaInst</tt> only
757 <i>requires</i> a (const-ptr-to) <tt>Type</tt>. Thus:
759 <pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
761 will create an <tt>AllocaInst</tt> instance that represents the
762 allocation of one integer in the current stack frame, at runtime.
763 Each <tt>Instruction</tt> subclass is likely to have varying default
764 parameters which change the semantics of the instruction, so refer to
765 the <a href="/doxygen/classInstruction.html">doxygen documentation for
766 the subclass of Instruction</a> that you're interested in
769 <p><i>Naming values</i></p>
772 It is very useful to name the values of instructions when you're able
773 to, as this facilitates the debugging of your transformations. If you
774 end up looking at generated LLVM machine code, you definitely want to
775 have logical names associated with the results of instructions! By
776 supplying a value for the <tt>Name</tt> (default) parameter of the
777 <tt>Instruction</tt> constructor, you associate a logical name with
778 the result of the instruction's execution at runtime. For example,
779 say that I'm writing a transformation that dynamically allocates space
780 for an integer on the stack, and that integer is going to be used as
781 some kind of index by some other code. To accomplish this, I place an
782 <tt>AllocaInst</tt> at the first point in the first
783 <tt>BasicBlock</tt> of some <tt>Function</tt>, and I'm intending to
784 use it within the same <tt>Function</tt>. I might do:
786 <pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
788 where <tt>indexLoc</tt> is now the logical name of the instruction's
789 execution value, which is a pointer to an integer on the runtime
793 <p><i>Inserting instructions</i></p>
796 There are essentially two ways to insert an <tt>Instruction</tt> into
797 an existing sequence of instructions that form a <tt>BasicBlock</tt>:
799 <li>Insertion into an explicit instruction list
801 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within
802 that <tt>BasicBlock</tt>, and a newly-created instruction
803 we wish to insert before <tt>*pi</tt>, we do the following:
806 BasicBlock* pb = ...;
807 Instruction* pi = ...;
808 Instruction* newInst = new Instruction(...);
809 pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb
813 <li>Insertion into an implicit instruction list
814 <p><tt>Instruction</tt> instances that are already in
815 <tt>BasicBlock</tt>s are implicitly associated with an existing
816 instruction list: the instruction list of the enclosing basic block.
817 Thus, we could have accomplished the same thing as the above code
818 without being given a <tt>BasicBlock</tt> by doing:
820 Instruction* pi = ...;
821 Instruction* newInst = new Instruction(...);
822 pi->getParent()->getInstList().insert(pi, newInst);
824 In fact, this sequence of steps occurs so frequently that the
825 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes
826 provide constructors which take (as a default parameter) a pointer to
827 an <tt>Instruction</tt> which the newly-created <tt>Instruction</tt>
828 should precede. That is, <tt>Instruction</tt> constructors are
829 capable of inserting the newly-created instance into the
830 <tt>BasicBlock</tt> of a provided instruction, immediately before that
831 instruction. Using an <tt>Instruction</tt> constructor with a
832 <tt>insertBefore</tt> (default) parameter, the above code becomes:
834 Instruction* pi = ...;
835 Instruction* newInst = new Instruction(..., pi);
837 which is much cleaner, especially if you're creating a lot of
838 instructions and adding them to <tt>BasicBlock</tt>s.
843 <!--_______________________________________________________________________-->
844 </ul><h4><a name="schanges_deleting"><hr size=0>Deleting
845 <tt>Instruction</tt>s</h4><ul>
847 Deleting an instruction from an existing sequence of instructions that form a <a
848 href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First, you
849 must have a pointer to the instruction that you wish to delete. Second, you
850 need to obtain the pointer to that instruction's basic block. You use the
851 pointer to the basic block to get its list of instructions and then use the
852 erase function to remove your instruction.<p>
857 <a href="#Instruction">Instruction</a> *I = .. ;
858 <a href="#BasicBlock">BasicBlock</a> *BB = I->getParent();
859 BB->getInstList().erase(I);
862 <!--_______________________________________________________________________-->
863 </ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
864 <tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
866 <p><i>Replacing individual instructions</i></p>
869 href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h
870 </a>" permits use of two very useful replace functions:
871 <tt>ReplaceInstWithValue</tt> and <tt>ReplaceInstWithInst</tt>.
875 <li><tt>ReplaceInstWithValue</tt>
877 <p>This function replaces all uses (within a basic block) of a given
878 instruction with a value, and then removes the original instruction.
879 The following example illustrates the replacement of the result of a
880 particular <tt>AllocaInst</tt> that allocates memory for a single
881 integer with an null pointer to an integer.</p>
884 AllocaInst* instToReplace = ...;
885 ReplaceInstWithValue(*instToReplace->getParent(), instToReplace,
886 Constant::getNullValue(PointerType::get(Type::IntTy)));
889 <li><tt>ReplaceInstWithInst</tt>
891 <p>This function replaces a particular instruction with another
892 instruction. The following example illustrates the replacement of one
893 <tt>AllocaInst</tt> with another.<p>
896 AllocaInst* instToReplace = ...;
897 ReplaceInstWithInst(*instToReplace->getParent(), instToReplace,
898 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt");
902 <p><i>Replacing multiple uses of <tt>User</tt>s and
903 <tt>Value</tt>s</i></p>
905 You can use <tt>Value::replaceAllUsesWith</tt> and
906 <tt>User::replaceUsesOfWith</tt> to change more than one use at a
907 time. See the doxygen documentation for the <a
908 href="/doxygen/classValue.html">Value Class</a> and <a
909 href="/doxygen/classUser.html">User Class</a>, respectively, for more
912 <!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
913 include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
914 ReplaceInstWithValue, ReplaceInstWithInst
917 <!-- *********************************************************************** -->
918 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
919 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
920 <a name="coreclasses">The Core LLVM Class Hierarchy Reference
921 </b></font></td></tr></table><ul>
922 <!-- *********************************************************************** -->
924 The Core LLVM classes are the primary means of representing the program being
925 inspected or transformed. The core LLVM classes are defined in header files in
926 the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
930 <!-- ======================================================================= -->
931 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
932 <tr><td> </td><td width="100%">
933 <font color="#EEEEFF" face="Georgia,Palatino"><b>
934 <a name="Value">The <tt>Value</tt> class</a>
935 </b></font></td></tr></table><ul>
937 <tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
938 doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
941 The <tt>Value</tt> class is the most important class in LLVM Source base. It
942 represents a typed value that may be used (among other things) as an operand to
943 an instruction. There are many different types of <tt>Value</tt>s, such as <a
944 href="#Constant"><tt>Constant</tt></a>s, <a
945 href="#Argument"><tt>Argument</tt></a>s, and even <a
946 href="#Instruction"><tt>Instruction</tt></a>s and <a
947 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
949 A particular <tt>Value</tt> may be used many times in the LLVM representation
950 for a program. For example, an incoming argument to a function (represented
951 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
952 every instruction in the function that references the argument. To keep track
953 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
954 href="#User"><tt>User</tt></a>s that is using it (the <a
955 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
956 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
957 def-use information in the program, and is accessible through the <tt>use_</tt>*
958 methods, shown below.<p>
960 Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
961 this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
962 method. <a name="#nameWarning">In addition, all LLVM values can be named. The
963 "name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
966 %<b>foo</b> = add int 1, 2
969 The name of this instruction is "foo". <b>NOTE</b> that the name of any value
970 may be missing (an empty string), so names should <b>ONLY</b> be used for
971 debugging (making the source code easier to read, debugging printouts), they
972 should not be used to keep track of values or map between them. For this
973 purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
976 One important aspect of LLVM is that there is no distinction between an SSA
977 variable and the operation that produces it. Because of this, any reference to
978 the value produced by an instruction (or the value available as an incoming
979 argument, for example) is represented as a direct pointer to the class that
980 represents this value. Although this may take some getting used to, it
981 simplifies the representation and makes it easier to manipulate.<p>
984 <!-- _______________________________________________________________________ -->
985 </ul><h4><a name="m_Value"><hr size=0>Important Public Members of
986 the <tt>Value</tt> class</h4><ul>
988 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
989 <tt>Value::use_const_iterator</tt>
990 - Typedef for const_iterator over the use-list<br>
991 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
992 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
993 <tt>use_iterator use_begin()</tt>
994 - Get an iterator to the start of the use-list.<br>
995 <tt>use_iterator use_end()</tt>
996 - Get an iterator to the end of the use-list.<br>
997 <tt><a href="#User">User</a> *use_back()</tt>
998 - Returns the last element in the list.<p>
1000 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>
1002 <li><tt><a href="#Type">Type</a> *getType() const</tt><p>
1003 This method returns the Type of the Value.
1005 <li><tt>bool hasName() const</tt><br>
1006 <tt>std::string getName() const</tt><br>
1007 <tt>void setName(const std::string &Name)</tt><p>
1009 This family of methods is used to access and assign a name to a <tt>Value</tt>,
1010 be aware of the <a href="#nameWarning">precaution above</a>.<p>
1013 <li><tt>void replaceAllUsesWith(Value *V)</tt><p>
1015 This method traverses the use list of a <tt>Value</tt> changing all <a
1016 href="#User"><tt>User</tt>s</a> of the current value to refer to "<tt>V</tt>"
1017 instead. For example, if you detect that an instruction always produces a
1018 constant value (for example through constant folding), you can replace all uses
1019 of the instruction with the constant like this:<p>
1022 Inst->replaceAllUsesWith(ConstVal);
1027 <!-- ======================================================================= -->
1028 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1029 <tr><td> </td><td width="100%">
1030 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1031 <a name="User">The <tt>User</tt> class</a>
1032 </b></font></td></tr></table><ul>
1034 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
1035 doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
1036 Superclass: <a href="#Value"><tt>Value</tt></a><p>
1039 The <tt>User</tt> class is the common base class of all LLVM nodes that may
1040 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
1041 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
1042 referring to. The <tt>User</tt> class itself is a subclass of
1045 The operands of a <tt>User</tt> point directly to the LLVM <a
1046 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
1047 Single Assignment (SSA) form, there can only be one definition referred to,
1048 allowing this direct connection. This connection provides the use-def
1049 information in LLVM.<p>
1051 <!-- _______________________________________________________________________ -->
1052 </ul><h4><a name="m_User"><hr size=0>Important Public Members of
1053 the <tt>User</tt> class</h4><ul>
1055 The <tt>User</tt> class exposes the operand list in two ways: through an index
1056 access interface and through an iterator based interface.<p>
1058 <li><tt>Value *getOperand(unsigned i)</tt><br>
1059 <tt>unsigned getNumOperands()</tt><p>
1061 These two methods expose the operands of the <tt>User</tt> in a convenient form
1062 for direct access.<p>
1064 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
1065 <tt>User::op_const_iterator</tt>
1066 <tt>use_iterator op_begin()</tt>
1067 - Get an iterator to the start of the operand list.<br>
1068 <tt>use_iterator op_end()</tt>
1069 - Get an iterator to the end of the operand list.<p>
1071 Together, these methods make up the iterator based interface to the operands of
1076 <!-- ======================================================================= -->
1077 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1078 <tr><td> </td><td width="100%">
1079 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1080 <a name="Instruction">The <tt>Instruction</tt> class</a>
1081 </b></font></td></tr></table><ul>
1084 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
1085 doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
1086 Superclasses: <a href="#User"><tt>User</tt></a>, <a
1087 href="#Value"><tt>Value</tt></a><p>
1089 The <tt>Instruction</tt> class is the common base class for all LLVM
1090 instructions. It provides only a few methods, but is a very commonly used
1091 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
1092 opcode (instruction type) and the parent <a
1093 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
1094 into. To represent a specific type of instruction, one of many subclasses of
1095 <tt>Instruction</tt> are used.<p>
1097 Because the <tt>Instruction</tt> class subclasses the <a
1098 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
1099 way as for other <a href="#User"><tt>User</tt></a>s (with the
1100 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
1101 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
1103 An important file for the <tt>Instruction</tt> class is the
1104 <tt>llvm/Instruction.def</tt> file. This file contains some meta-data about the
1105 various different types of instructions in LLVM. It describes the enum values
1106 that are used as opcodes (for example <tt>Instruction::Add</tt> and
1107 <tt>Instruction::SetLE</tt>), as well as the concrete sub-classes of
1108 <tt>Instruction</tt> that implement the instruction (for example <tt><a
1109 href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
1110 href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
1111 this file confused doxygen, so these enum values don't show up correctly in the
1112 <a href="/doxygen/classInstruction.html">doxygen output</a>.<p>
1115 <!-- _______________________________________________________________________ -->
1116 </ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
1117 the <tt>Instruction</tt> class</h4><ul>
1119 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
1121 Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
1122 <tt>Instruction</tt> is embedded into.<p>
1124 <li><tt>bool hasSideEffects()</tt><p>
1126 Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
1127 <tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
1129 <li><tt>unsigned getOpcode()</tt><p>
1131 Returns the opcode for the <tt>Instruction</tt>.<p>
1133 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt><p>
1135 Returns another instance of the specified instruction, identical in all ways to
1136 the original except that the instruction has no parent (ie it's not embedded
1137 into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>), and it has no name.<p>
1143 \subsection{Subclasses of Instruction :}
1145 <li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
1147 <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.
1149 <li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
1151 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
1152 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
1153 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
1156 <li>PHINode : This represents the PHI instructions in the SSA form.
1158 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
1159 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
1160 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
1161 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
1162 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
1163 Add an incoming value to the end of the PHI list
1164 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
1165 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
1167 <li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
1168 <li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
1170 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
1172 <li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
1174 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
1176 <li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
1178 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
1179 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
1180 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
1188 <!-- ======================================================================= -->
1189 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1190 <tr><td> </td><td width="100%">
1191 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1192 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
1193 </b></font></td></tr></table><ul>
1196 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
1197 doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
1198 Superclass: <a href="#Value"><tt>Value</tt></a><p>
1201 This class represents a single entry multiple exit section of the code, commonly
1202 known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
1203 maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
1204 the body of the block. Matching the language definition, the last element of
1205 this list of instructions is always a terminator instruction (a subclass of the
1206 <a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
1208 In addition to tracking the list of instructions that make up the block, the
1209 <tt>BasicBlock</tt> class also keeps track of the <a
1210 href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
1212 Note that <tt>BasicBlock</tt>s themselves are <a
1213 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
1214 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
1218 <!-- _______________________________________________________________________ -->
1219 </ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
1220 the <tt>BasicBlock</tt> class</h4><ul>
1222 <li><tt>BasicBlock(const std::string &Name = "", <a
1223 href="#Function">Function</a> *Parent = 0)</tt><p>
1225 The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
1226 insertion into a function. The constructor simply takes a name for the new
1227 block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
1228 into. If the <tt>Parent</tt> parameter is specified, the new
1229 <tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
1230 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
1231 manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
1233 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
1234 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
1235 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1236 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1238 These methods and typedefs are forwarding functions that have the same semantics
1239 as the standard library methods of the same names. These methods expose the
1240 underlying instruction list of a basic block in a way that is easy to
1241 manipulate. To get the full complement of container operations (including
1242 operations to update the list), you must use the <tt>getInstList()</tt>
1245 <li><tt>BasicBlock::InstListType &getInstList()</tt><p>
1247 This method is used to get access to the underlying container that actually
1248 holds the Instructions. This method must be used when there isn't a forwarding
1249 function in the <tt>BasicBlock</tt> class for the operation that you would like
1250 to perform. Because there are no forwarding functions for "updating"
1251 operations, you need to use this if you want to update the contents of a
1252 <tt>BasicBlock</tt>.<p>
1254 <li><tt><A href="#Function">Function</a> *getParent()</tt><p>
1256 Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
1257 embedded into, or a null pointer if it is homeless.<p>
1259 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
1261 Returns a pointer to the terminator instruction that appears at the end of the
1262 <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
1263 instruction in the block is not a terminator, then a null pointer is
1267 <!-- ======================================================================= -->
1268 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1269 <tr><td> </td><td width="100%">
1270 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1271 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
1272 </b></font></td></tr></table><ul>
1275 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
1276 doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
1277 Superclasses: <a href="#User"><tt>User</tt></a>, <a
1278 href="#Value"><tt>Value</tt></a><p>
1280 Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
1281 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
1282 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
1283 Because they are visible at global scope, they are also subject to linking with
1284 other globals defined in different translation units. To control the linking
1285 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
1286 <tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
1288 If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
1289 <tt>static</tt> in C), it is not visible to code outside the current translation
1290 unit, and does not participate in linking. If it has external linkage, it is
1291 visible to external code, and does participate in linking. In addition to
1292 linkage information, <tt>GlobalValue</tt>s keep track of which <a
1293 href="#Module"><tt>Module</tt></a> they are currently part of.<p>
1295 Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
1296 their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
1297 always a pointer to its contents. This is explained in the LLVM Language
1298 Reference Manual.<p>
1301 <!-- _______________________________________________________________________ -->
1302 </ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
1303 the <tt>GlobalValue</tt> class</h4><ul>
1305 <li><tt>bool hasInternalLinkage() const</tt><br>
1306 <tt>bool hasExternalLinkage() const</tt><br>
1307 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
1309 These methods manipulate the linkage characteristics of the
1310 <tt>GlobalValue</tt>.<p>
1312 <li><tt><a href="#Module">Module</a> *getParent()</tt><p>
1314 This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
1315 currently embedded into.<p>
1319 <!-- ======================================================================= -->
1320 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1321 <tr><td> </td><td width="100%">
1322 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1323 <a name="Function">The <tt>Function</tt> class</a>
1324 </b></font></td></tr></table><ul>
1327 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
1328 doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
1329 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1330 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1332 The <tt>Function</tt> class represents a single procedure in LLVM. It is
1333 actually one of the more complex classes in the LLVM heirarchy because it must
1334 keep track of a large amount of data. The <tt>Function</tt> class keeps track
1335 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
1336 href="#Argument"><tt>Argument</tt></a>s, and a <a
1337 href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
1339 The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
1340 used part of <tt>Function</tt> objects. The list imposes an implicit ordering
1341 of the blocks in the function, which indicate how the code will be layed out by
1342 the backend. Additionally, the first <a
1343 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
1344 <tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
1345 block. There are no implicit exit nodes, and in fact there may be multiple exit
1346 nodes from a single <tt>Function</tt>. If the <a
1347 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
1348 the <tt>Function</tt> is actually a function declaration: the actual body of the
1349 function hasn't been linked in yet.<p>
1351 In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
1352 <tt>Function</tt> class also keeps track of the list of formal <a
1353 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
1354 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
1355 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
1356 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
1358 The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
1359 feature that is only used when you have to look up a value by name. Aside from
1360 that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
1361 make sure that there are not conflicts between the names of <a
1362 href="#Instruction"><tt>Instruction</tt></a>s, <a
1363 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
1364 href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
1367 <!-- _______________________________________________________________________ -->
1368 </ul><h4><a name="m_Function"><hr size=0>Important Public Members of
1369 the <tt>Function</tt> class</h4><ul>
1371 <li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
1373 Constructor used when you need to create new <tt>Function</tt>s to add the the
1374 program. The constructor must specify the type of the function to create and
1375 whether or not it should start out with internal or external linkage.<p>
1377 <li><tt>bool isExternal()</tt><p>
1379 Return whether or not the <tt>Function</tt> has a body defined. If the function
1380 is "external", it does not have a body, and thus must be resolved by linking
1381 with a function defined in a different translation unit.<p>
1384 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
1385 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
1386 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1387 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1389 These are forwarding methods that make it easy to access the contents of a
1390 <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1393 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
1395 Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
1396 neccesary to use when you need to update the list or perform a complex action
1397 that doesn't have a forwarding method.<p>
1400 <li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
1401 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
1402 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
1403 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
1405 These are forwarding methods that make it easy to access the contents of a
1406 <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
1408 <li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
1410 Returns the list of <a href="#Argument"><tt>Argument</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>
1416 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
1418 Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1419 function. Because the entry block for the function is always the first block,
1420 this returns the first block of the <tt>Function</tt>.<p>
1422 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1423 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
1425 This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
1426 and returns the return type of the function, or the <a
1427 href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
1430 <li><tt>bool hasSymbolTable() const</tt><p>
1432 Return true if the <tt>Function</tt> has a symbol table allocated to it and if
1433 there is at least one entry in it.<p>
1435 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1437 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1438 <tt>Function</tt> or a null pointer if one has not been allocated (because there
1439 are no named values in the function).<p>
1441 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
1443 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1444 <tt>Function</tt> or allocate a new <a
1445 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
1446 should only be used when adding elements to the <a
1447 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
1448 not left laying around.<p>
1452 <!-- ======================================================================= -->
1453 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1454 <tr><td> </td><td width="100%">
1455 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1456 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1457 </b></font></td></tr></table><ul>
1460 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
1461 doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
1462 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1463 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1465 Global variables are represented with the (suprise suprise)
1466 <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
1467 also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
1468 are always referenced by their address (global values must live in memory, so
1469 their "name" refers to their address). Global variables may have an initial
1470 value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
1471 have an initializer, they may be marked as "constant" themselves (indicating
1472 that their contents never change at runtime).<p>
1475 <!-- _______________________________________________________________________ -->
1476 </ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
1477 <tt>GlobalVariable</tt> class</h4><ul>
1479 <li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
1480 isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
1481 &Name = "")</tt><p>
1483 Create a new global variable of the specified type. If <tt>isConstant</tt> is
1484 true then the global variable will be marked as unchanging for the program, and
1485 if <tt>isInternal</tt> is true the resultant global variable will have internal
1486 linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
1489 <li><tt>bool isConstant() const</tt><p>
1491 Returns true if this is a global variable is known not to be modified at
1495 <li><tt>bool hasInitializer()</tt><p>
1497 Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
1500 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
1502 Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
1503 this method if there is no initializer.<p>
1506 <!-- ======================================================================= -->
1507 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1508 <tr><td> </td><td width="100%">
1509 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1510 <a name="Module">The <tt>Module</tt> class</a>
1511 </b></font></td></tr></table><ul>
1514 href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
1515 doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
1517 The <tt>Module</tt> class represents the top level structure present in LLVM
1518 programs. An LLVM module is effectively either a translation unit of the
1519 original program or a combination of several translation units merged by the
1520 linker. The <tt>Module</tt> class keeps track of a list of <a
1521 href="#Function"><tt>Function</tt></a>s, a list of <a
1522 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1523 href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1524 helpful member functions that try to make common operations easy.<p>
1527 <!-- _______________________________________________________________________ -->
1528 </ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
1529 <tt>Module</tt> class</h4><ul>
1531 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
1532 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
1533 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1534 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1536 These are forwarding methods that make it easy to access the contents of a
1537 <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1540 <li><tt>Module::FunctionListType &getFunctionList()</tt><p>
1542 Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1543 neccesary to use when you need to update the list or perform a complex action
1544 that doesn't have a forwarding method.<p>
1546 <!-- Global Variable -->
1549 <li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
1550 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
1551 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
1552 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
1554 These are forwarding methods that make it easy to access the contents of a
1555 <tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
1558 <li><tt>Module::GlobalListType &getGlobalList()</tt><p>
1560 Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
1561 This is neccesary to use when you need to update the list or perform a complex
1562 action that doesn't have a forwarding method.<p>
1565 <!-- Symbol table stuff -->
1568 <li><tt>bool hasSymbolTable() const</tt><p>
1570 Return true if the <tt>Module</tt> has a symbol table allocated to it and if
1571 there is at least one entry in it.<p>
1573 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1575 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1576 <tt>Module</tt> or a null pointer if one has not been allocated (because there
1577 are no named values in the function).<p>
1579 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
1581 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1582 <tt>Module</tt> or allocate a new <a
1583 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
1584 should only be used when adding elements to the <a
1585 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
1586 not left laying around.<p>
1589 <!-- Convenience methods -->
1592 <li><tt><a href="#Function">Function</a> *getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
1594 Look up the specified function in the <tt>Module</tt> <a
1595 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
1599 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
1600 &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
1602 Look up the specified function in the <tt>Module</tt> <a
1603 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
1604 external declaration for the function and return it.<p>
1607 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
1609 If there is at least one entry in the <a
1610 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
1611 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
1615 <li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
1618 Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
1619 <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
1620 is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
1624 <!-- ======================================================================= -->
1625 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1626 <tr><td> </td><td width="100%">
1627 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1628 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
1629 </b></font></td></tr></table><ul>
1631 Constant represents a base class for different types of constants. It is
1632 subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
1633 ConstantArray etc for representing the various types of Constants.<p>
1636 <!-- _______________________________________________________________________ -->
1637 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1639 <li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
1644 \subsection{Important Subclasses of Constant}
1646 <li>ConstantSInt : This subclass of Constant represents a signed integer constant.
1648 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
1650 <li>ConstantUInt : This class represents an unsigned integer.
1652 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
1654 <li>ConstantFP : This class represents a floating point constant.
1656 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
1658 <li>ConstantBool : This represents a boolean constant.
1660 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
1662 <li>ConstantArray : This represents a constant array.
1664 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1666 <li>ConstantStruct : This represents a constant struct.
1668 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1670 <li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
1672 <li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
1677 <!-- ======================================================================= -->
1678 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1679 <tr><td> </td><td width="100%">
1680 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1681 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
1682 </b></font></td></tr></table><ul>
1684 Type as noted earlier is also a subclass of a Value class. Any primitive
1685 type (like int, short etc) in LLVM is an instance of Type Class. All
1686 other types are instances of subclasses of type like FunctionType,
1687 ArrayType etc. DerivedType is the interface for all such dervied types
1688 including FunctionType, ArrayType, PointerType, StructType. Types can have
1689 names. They can be recursive (StructType). There exists exactly one instance
1690 of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
1692 <!-- _______________________________________________________________________ -->
1693 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1695 <li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
1696 <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.
1697 <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.
1698 <li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
1699 <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.
1701 <li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
1702 <li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
1703 <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.
1704 <li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
1705 <li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
1706 <li><tt>const Type * getContainedType (unsigned i) const</tt>:
1707 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.
1708 <li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
1712 \subsection{Derived Types}
1714 <li>SequentialType : This is subclassed by ArrayType and PointerType
1716 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
1718 <li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
1720 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
1722 <li>PointerType : Subclass of SequentialType for pointer types.
1723 <li>StructType : subclass of DerivedTypes for struct types
1724 <li>FunctionType : subclass of DerivedTypes for function types.
1727 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
1728 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
1729 <li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
1730 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
1731 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
1738 <!-- ======================================================================= -->
1739 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1740 <tr><td> </td><td width="100%">
1741 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1742 <a name="Argument">The <tt>Argument</tt> class</a>
1743 </b></font></td></tr></table><ul>
1745 This subclass of Value defines the interface for incoming formal arguments to a
1746 function. A Function maitanis a list of its formal arguments. An argument has a
1747 pointer to the parent Function.
1752 <!-- *********************************************************************** -->
1754 <!-- *********************************************************************** -->
1757 <address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
1758 <a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
1759 <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
1760 <!-- hhmts start -->
1761 Last modified: Sun Sep 22 14:38:05 CDT 2002
1763 </font></body></html>