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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>
15 <li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt> and
16 <tt>dyn_cast<></tt> templates</a>
18 <li><a href="#common">Helpful Hints for Common Operations</a>
20 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
22 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
23 in a <tt>Function</tt></a>
24 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
25 in a <tt>BasicBlock</tt></a>
26 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
27 in a <tt>Function</tt></a>
28 <li><a href="#iterate_convert">Turning an iterator into a class
30 <li><a href="#iterate_complex">Finding call sites: a more complex
32 <li><a href="#iterate_chains">Iterating over def-use & use-def
35 <li><a href="#simplechanges">Making simple changes</a>
37 <li>Creating and inserting new <tt>Instruction</tt>s
38 <li>Deleting <tt>Instruction</tt>s
39 <li>Replacing an <tt>Instruction</tt> with another <tt>Value</tt>
42 <li>Working with the Control Flow Graph
44 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
50 <li>The general graph API
51 <li>The <tt>InstVisitor</tt> template
53 <li>The <tt>Statistic</tt> template
57 <li>Useful related topics
59 <li>The <tt>-time-passes</tt> option
60 <li>How to use the LLVM Makefile system
61 <li>How to write a regression test
66 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
68 <li><a href="#Value">The <tt>Value</tt> class</a>
70 <li><a href="#User">The <tt>User</tt> class</a>
72 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
76 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
78 <li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a>
79 <li><a href="#Function">The <tt>Function</tt> class</a>
80 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a>
82 <li><a href="#Module">The <tt>Module</tt> class</a>
83 <li><a href="#Constant">The <tt>Constant</tt> class</a>
89 <li><a href="#Type">The <tt>Type</tt> class</a>
90 <li><a href="#Argument">The <tt>Argument</tt> class</a>
92 <li>The <tt>SymbolTable</tt> class
93 <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
95 <li>Creating, inserting, moving and deleting from LLVM lists
97 <li>Important iterator invalidation semantics to be aware of
100 <p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
101 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>, and
102 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a></b><p>
106 <!-- *********************************************************************** -->
107 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
108 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
109 <a name="introduction">Introduction
110 </b></font></td></tr></table><ul>
111 <!-- *********************************************************************** -->
113 This document is meant to highlight some of the important classes and interfaces
114 available in the LLVM source-base. This manual is not intended to explain what
115 LLVM is, how it works, and what LLVM code looks like. It assumes that you know
116 the basics of LLVM and are interested in writing transformations or otherwise
117 analyzing or manipulating the code.<p>
119 This document should get you oriented so that you can find your way in the
120 continuously growing source code that makes up the LLVM infrastructure. Note
121 that this manual is not intended to serve as a replacement for reading the
122 source code, so if you think there should be a method in one of these classes to
123 do something, but it's not listed, check the source. Links to the <a
124 href="/doxygen/">doxygen</a> sources are provided to make this as easy as
127 The first section of this document describes general information that is useful
128 to know when working in the LLVM infrastructure, and the second describes the
129 Core LLVM classes. In the future this manual will be extended with information
130 describing how to use extension libraries, such as dominator information, CFG
131 traversal routines, and useful utilities like the <tt><a
132 href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
135 <!-- *********************************************************************** -->
136 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
137 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
138 <a name="general">General Information
139 </b></font></td></tr></table><ul>
140 <!-- *********************************************************************** -->
142 This section contains general information that is useful if you are working in
143 the LLVM source-base, but that isn't specific to any particular API.<p>
146 <!-- ======================================================================= -->
147 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
148 <tr><td> </td><td width="100%">
149 <font color="#EEEEFF" face="Georgia,Palatino"><b>
150 <a name="stl">The C++ Standard Template Library</a>
151 </b></font></td></tr></table><ul>
153 LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
154 more than you are used to, or have seen before. Because of this, you might want
155 to do a little background reading in the techniques used and capabilities of the
156 library. There are many good pages that discuss the STL, and several books on
157 the subject that you can get, so it will not be discussed in this document.<p>
159 Here are some useful links:<p>
161 <li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
162 Library reference</a> - an excellent reference for the STL and other parts of
163 the standard C++ library.<br>
165 <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
168 <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
170 href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
173 <li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
178 You are also encouraged to take a look at the <a
179 href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
180 to write maintainable code more than where to put your curly braces.<p>
183 <!-- ======================================================================= -->
184 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
185 <tr><td> </td><td width="100%">
186 <font color="#EEEEFF" face="Georgia,Palatino"><b>
187 <a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
188 </b></font></td></tr></table><ul>
190 The LLVM source-base makes extensive use of a custom form of RTTI. These
191 templates have many similarities to the C++ <tt>dynamic_cast<></tt>
192 operator, but they don't have some drawbacks (primarily stemming from the fact
193 that <tt>dynamic_cast<></tt> only works on classes that have a v-table).
194 Because they are used so often, you must know what they do and how they work.
195 All of these templates are defined in the <a
196 href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a> file (note
197 that you very rarely have to include this file directly).<p>
201 <dt><tt>isa<></tt>:
203 <dd>The <tt>isa<></tt> operator works exactly like the Java
204 "<tt>instanceof</tt>" operator. It returns true or false depending on whether a
205 reference or pointer points to an instance of the specified class. This can be
206 very useful for constraint checking of various sorts (example below).<p>
209 <dt><tt>cast<></tt>:
211 <dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
212 converts a pointer or reference from a base class to a derived cast, causing an
213 assertion failure if it is not really an instance of the right type. This
214 should be used in cases where you have some information that makes you believe
215 that something is of the right type. An example of the <tt>isa<></tt> and
216 <tt>cast<></tt> template is:<p>
219 static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
220 if (isa<<a href="#Constant">Constant</a>>(V) || isa<<a href="#Argument">Argument</a>>(V) || isa<<a href="#GlobalValue">GlobalValue</a>>(V))
223 <i>// Otherwise, it must be an instruction...</i>
224 return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
227 Note that you should <b>not</b> use an <tt>isa<></tt> test followed by a
228 <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt> operator.<p>
231 <dt><tt>dyn_cast<></tt>:
233 <dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
234 checks to see if the operand is of the specified type, and if so, returns a
235 pointer to it (this operator does not work with references). If the operand is
236 not of the correct type, a null pointer is returned. Thus, this works very much
237 like the <tt>dynamic_cast</tt> operator in C++, and should be used in the same
238 circumstances. Typically, the <tt>dyn_cast<></tt> operator is used in an
239 <tt>if</tt> statement or some other flow control statement like this:<p>
242 if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
247 This form of the <tt>if</tt> statement effectively combines together a call to
248 <tt>isa<></tt> and a call to <tt>cast<></tt> into one statement,
249 which is very convenient.<p>
251 Another common example is:<p>
254 <i>// Loop over all of the phi nodes in a basic block</i>
255 BasicBlock::iterator BBI = BB->begin();
256 for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(&*BBI); ++BBI)
260 Note that the <tt>dyn_cast<></tt> operator, like C++'s
261 <tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused. In
262 particular you should not use big chained <tt>if/then/else</tt> blocks to check
263 for lots of different variants of classes. If you find yourself wanting to do
264 this, it is much cleaner and more efficient to use the InstVisitor class to
265 dispatch over the instruction type directly.<p>
268 <dt><tt>cast_or_null<></tt>:
270 <dd>The <tt>cast_or_null<></tt> operator works just like the
271 <tt>cast<></tt> operator, except that it allows for a null pointer as an
272 argument (which it then propogates). This can sometimes be useful, allowing you
273 to combine several null checks into one.<p>
276 <dt><tt>dyn_cast_or_null<></tt>:
278 <dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
279 <tt>dyn_cast<></tt> operator, except that it allows for a null pointer as
280 an argument (which it then propogates). This can sometimes be useful, allowing
281 you to combine several null checks into one.<p>
285 These five templates can be used with any classes, whether they have a v-table
286 or not. To add support for these templates, you simply need to add
287 <tt>classof</tt> static methods to the class you are interested casting to.
288 Describing this is currently outside the scope of this document, but there are
289 lots of examples in the LLVM sourcebase.<p>
293 <!-- *********************************************************************** -->
294 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
295 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
296 <a name="common">Helpful Hints for Common Operations
297 </b></font></td></tr></table><ul>
298 <!-- *********************************************************************** -->
300 This section describes how to perform some very simple transformations of LLVM
301 code. This is meant to give examples of common idioms used, showing the
302 practical side of LLVM transformations.<p>
304 Because this is a "how-to" section, you should also read about the main classes
305 that you will be working with. The <a href="#coreclasses">Core LLVM Class
306 Hierarchy Reference</a> contains details and descriptions of the main classes
307 that you should know about.<p>
309 <!-- NOTE: this section should be heavy on example code -->
312 <!-- ======================================================================= -->
313 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
314 <tr><td> </td><td width="100%">
315 <font color="#EEEEFF" face="Georgia,Palatino"><b>
316 <a name="inspection">Basic Inspection and Traversal Routines</a>
317 </b></font></td></tr></table><ul>
319 The LLVM compiler infrastructure have many different data structures that may be
320 traversed. Following the example of the C++ standard template library, the
321 techniques used to traverse these various data structures are all basically the
322 same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
323 method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
324 function returns an iterator pointing to one past the last valid element of the
325 sequence, and there is some <tt>XXXiterator</tt> data type that is common
326 between the two operations.<p>
328 Because the pattern for iteration is common across many different aspects of the
329 program representation, the standard template library algorithms may be used on
330 them, and it is easier to remember how to iterate. First we show a few common
331 examples of the data structures that need to be traversed. Other data
332 structures are traversed in very similar ways.<p>
335 <!-- _______________________________________________________________________ -->
336 </ul><h4><a name="iterate_function"><hr size=0>Iterating over the <a
337 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
338 href="#Function"><tt>Function</tt></a> </h4><ul>
340 It's quite common to have a <tt>Function</tt> instance that you'd like
341 to transform in some way; in particular, you'd like to manipulate its
342 <tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over
343 all of the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>.
344 The following is an example that prints the name of a
345 <tt>BasicBlock</tt> and the number of <tt>Instruction</tt>s it
349 // func is a pointer to a Function instance
350 for(Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {
352 // print out the name of the basic block if it has one, and then the
353 // number of instructions that it contains
355 cerr << "Basic block (name=" << i->getName() << ") has "
356 << i->size() << " instructions.\n";
360 Note that i can be used as if it were a pointer for the purposes of
361 invoking member functions of the <tt>Instruction</tt> class. This is
362 because the indirection operator is overloaded for the iterator
363 classes. In the above code, the expression <tt>i->size()</tt> is
364 exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.
366 <!-- _______________________________________________________________________ -->
367 </ul><h4><a name="iterate_basicblock"><hr size=0>Iterating over the <a
368 href="#Instruction"><tt>Instruction</tt></a>s in a <a
369 href="#BasicBlock"><tt>BasicBlock</tt></a> </h4><ul>
371 Just like when dealing with <tt>BasicBlock</tt>s in
372 <tt>Function</tt>s, it's easy to iterate over the individual
373 instructions that make up <tt>BasicBlock</tt>s. Here's a code snippet
374 that prints out each instruction in a <tt>BasicBlock</tt>:
377 // blk is a pointer to a BasicBlock instance
378 for(BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
379 // the next statement works since operator<<(ostream&,...)
380 // is overloaded for Instruction&
381 cerr << *i << "\n";
384 However, this isn't really the best way to print out the contents of a
385 <tt>BasicBlock</tt>! Since the ostream operators are overloaded for
386 virtually anything you'll care about, you could have just invoked the
387 print routine on the basic block itself: <tt>cerr << *blk <<
390 Note that currently operator<< is implemented for <tt>Value*</tt>, so it
391 will print out the contents of the pointer, instead of
392 the pointer value you might expect. This is a deprecated interface that will
393 be removed in the future, so it's best not to depend on it. To print out the
394 pointer value for now, you must cast to <tt>void*</tt>.<p>
397 <!-- _______________________________________________________________________ -->
398 </ul><h4><a name="iterate_institer"><hr size=0>Iterating over the <a
399 href="#Instruction"><tt>Instruction</tt></a>s in a <a
400 href="#Function"><tt>Function</tt></a></h4><ul>
402 If you're finding that you commonly iterate over a <tt>Function</tt>'s
403 <tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s
404 <tt>Instruction</tt>s, <tt>InstIterator</tt> should be used instead.
405 You'll need to include <a href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>, and then
406 instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
407 small example that shows how to dump all instructions in a function to
408 stderr (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
409 <tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&</tt>!):
412 #include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
414 // Suppose F is a ptr to a function
415 for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
416 cerr << **i << "\n";
419 Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
420 worklist with its initial contents. For example, if you wanted to
421 initialize a worklist to contain all instructions in a
422 <tt>Function</tt> F, all you would need to do is something like:
425 std::set<Instruction*> worklist;
426 worklist.insert(inst_begin(F), inst_end(F));
429 The STL set <tt>worklist</tt> would now contain all instructions in
430 the <tt>Function</tt> pointed to by F.
432 <!-- _______________________________________________________________________ -->
433 </ul><h4><a name="iterate_convert"><hr size=0>Turning an iterator into a class
434 pointer (and vice-versa) </h4><ul>
436 Sometimes, it'll be useful to grab a reference (or pointer) to a class
437 instance when all you've got at hand is an iterator. Well, extracting
438 a reference or a pointer from an iterator is very straightforward.
439 Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and
440 <tt>j</tt> is a <tt>BasicBlock::const_iterator</tt>:
443 Instruction& inst = *i; // grab reference to instruction reference
444 Instruction* pinst = &*i; // grab pointer to instruction reference
445 const Instruction& inst = *j;
447 However, the iterators you'll be working with in the LLVM framework
448 are special: they will automatically convert to a ptr-to-instance type
449 whenever they need to. Instead of dereferencing the iterator and then
450 taking the address of the result, you can simply assign the iterator
451 to the proper pointer type and you get the dereference and address-of
452 operation as a result of the assignment (behind the scenes, this is a
453 result of overloading casting mechanisms). Thus the last line of the
456 <pre>Instruction* pinst = &*i;</pre>
458 is semantically equivalent to
460 <pre>Instruction* pinst = i;</pre>
462 <b>Caveat emptor</b>: The above syntax works <i>only</i> when you're <i>not</i>
463 working with <tt>dyn_cast</tt>. The template definition of <tt><a
464 href="#isa">dyn_cast</a></tt> isn't implemented to handle this yet, so you'll
465 still need the following in order for things to work properly:
468 BasicBlock::iterator bbi = ...;
469 <a href="#BranchInst">BranchInst</a>* b = <a href="#isa">dyn_cast</a><<a href="#BranchInst">BranchInst</a>>(&*bbi);
472 It's also possible to turn a class pointer into the corresponding
473 iterator. Usually, this conversion is quite inexpensive. The
474 following code snippet illustrates use of the conversion constructors
475 provided by LLVM iterators. By using these, you can explicitly grab
476 the iterator of something without actually obtaining it via iteration
480 void printNextInstruction(Instruction* inst) {
481 BasicBlock::iterator it(inst);
482 ++it; // after this line, it refers to the instruction after *inst.
483 if(it != inst->getParent()->end()) cerr << *it << "\n";
486 Of course, this example is strictly pedagogical, because it'd be much
487 better to explicitly grab the next instruction directly from inst.
490 <!--_______________________________________________________________________-->
491 </ul><h4><a name="iterate_complex"><hr size=0>Finding call sites: a slightly
492 more complex example </h4><ul>
494 Say that you're writing a FunctionPass and would like to count all the
495 locations in the entire module (that is, across every
496 <tt>Function</tt>) where a certain function (i.e. some
497 <tt>Function</tt>*) already in scope. As you'll learn later, you may
498 want to use an <tt>InstVisitor</tt> to accomplish this in a much more
499 straightforward manner, but this example will allow us to explore how
500 you'd do it if you didn't have <tt>InstVisitor</tt> around. In
501 pseudocode, this is what we want to do:
504 initialize callCounter to zero
505 for each Function f in the Module
506 for each BasicBlock b in f
507 for each Instruction i in b
508 if(i is a CallInst and calls the given function)
509 increment callCounter
512 And the actual code is (remember, since we're writing a
513 <tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply
514 has to override the <tt>runOnFunction</tt> method...):
517 Function* targetFunc = ...;
519 class OurFunctionPass : public FunctionPass {
521 OurFunctionPass(): callCounter(0) { }
523 virtual runOnFunction(Function& F) {
524 for(Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
525 for(BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {
526 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a href="#CallInst">CallInst</a>>(&*inst)) {
527 // we know we've encountered a call instruction, so we
528 // need to determine if it's a call to the
529 // function pointed to by m_func or not.
531 if(callInst->getCalledFunction() == targetFunc)
538 unsigned callCounter;
542 <!--_______________________________________________________________________-->
543 </ul><h4><a name="iterate_chains"><hr size=0>Iterating over def-use &
544 use-def chains</h4><ul>
547 def-use chains ("finding all users of"): Value::use_begin/use_end
548 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
551 <!-- ======================================================================= -->
552 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
553 <tr><td> </td><td width="100%">
554 <font color="#EEEEFF" face="Georgia,Palatino"><b>
555 <a name="simplechanges">Making simple changes</a>
556 </b></font></td></tr></table><ul>
558 <!-- Value::replaceAllUsesWith
559 User::replaceUsesOfWith
560 Point out: include/llvm/Transforms/Utils/
561 especially BasicBlockUtils.h with:
562 ReplaceInstWithValue, ReplaceInstWithInst
567 <!-- *********************************************************************** -->
568 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
569 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
570 <a name="coreclasses">The Core LLVM Class Hierarchy Reference
571 </b></font></td></tr></table><ul>
572 <!-- *********************************************************************** -->
574 The Core LLVM classes are the primary means of representing the program being
575 inspected or transformed. The core LLVM classes are defined in header files in
576 the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
580 <!-- ======================================================================= -->
581 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
582 <tr><td> </td><td width="100%">
583 <font color="#EEEEFF" face="Georgia,Palatino"><b>
584 <a name="Value">The <tt>Value</tt> class</a>
585 </b></font></td></tr></table><ul>
587 <tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
588 doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
591 The <tt>Value</tt> class is the most important class in LLVM Source base. It
592 represents a typed value that may be used (among other things) as an operand to
593 an instruction. There are many different types of <tt>Value</tt>s, such as <a
594 href="#Constant"><tt>Constant</tt></a>s, <a
595 href="#Argument"><tt>Argument</tt></a>s, and even <a
596 href="#Instruction"><tt>Instruction</tt></a>s and <a
597 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
599 A particular <tt>Value</tt> may be used many times in the LLVM representation
600 for a program. For example, an incoming argument to a function (represented
601 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
602 every instruction in the function that references the argument. To keep track
603 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
604 href="#User"><tt>User</tt></a>s that is using it (the <a
605 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
606 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
607 def-use information in the program, and is accessible through the <tt>use_</tt>*
608 methods, shown below.<p>
610 Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
611 this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
612 method. <a name="#nameWarning">In addition, all LLVM values can be named. The
613 "name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
616 %<b>foo</b> = add int 1, 2
619 The name of this instruction is "foo". <b>NOTE</b> that the name of any value
620 may be missing (an empty string), so names should <b>ONLY</b> be used for
621 debugging (making the source code easier to read, debugging printouts), they
622 should not be used to keep track of values or map between them. For this
623 purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
626 One important aspect of LLVM is that there is no distinction between an SSA
627 variable and the operation that produces it. Because of this, any reference to
628 the value produced by an instruction (or the value available as an incoming
629 argument, for example) is represented as a direct pointer to the class that
630 represents this value. Although this may take some getting used to, it
631 simplifies the representation and makes it easier to manipulate.<p>
634 <!-- _______________________________________________________________________ -->
635 </ul><h4><a name="m_Value"><hr size=0>Important Public Members of
636 the <tt>Value</tt> class</h4><ul>
638 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
639 <tt>Value::use_const_iterator</tt>
640 - Typedef for const_iterator over the use-list<br>
641 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
642 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
643 <tt>use_iterator use_begin()</tt>
644 - Get an iterator to the start of the use-list.<br>
645 <tt>use_iterator use_end()</tt>
646 - Get an iterator to the end of the use-list.<br>
647 <tt><a href="#User">User</a> *use_back()</tt>
648 - Returns the last element in the list.<p>
650 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>
652 <li><tt><a href="#Type">Type</a> *getType() const</tt><p>
653 This method returns the Type of the Value.
655 <li><tt>bool hasName() const</tt><br>
656 <tt>std::string getName() const</tt><br>
657 <tt>void setName(const std::string &Name)</tt><p>
659 This family of methods is used to access and assign a name to a <tt>Value</tt>,
660 be aware of the <a href="#nameWarning">precaution above</a>.<p>
663 <li><tt>void replaceAllUsesWith(Value *V)</tt><p>
665 This method traverses the use list of a <tt>Value</tt> changing all <a
666 href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
667 instead. For example, if you detect that an instruction always produces a
668 constant value (for example through constant folding), you can replace all uses
669 of the instruction with the constant like this:<p>
672 Inst->replaceAllUsesWith(ConstVal);
677 <!-- ======================================================================= -->
678 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
679 <tr><td> </td><td width="100%">
680 <font color="#EEEEFF" face="Georgia,Palatino"><b>
681 <a name="User">The <tt>User</tt> class</a>
682 </b></font></td></tr></table><ul>
684 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
685 doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
686 Superclass: <a href="#Value"><tt>Value</tt></a><p>
689 The <tt>User</tt> class is the common base class of all LLVM nodes that may
690 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
691 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
692 referring to. The <tt>User</tt> class itself is a subclass of
695 The operands of a <tt>User</tt> point directly to the LLVM <a
696 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
697 Single Assignment (SSA) form, there can only be one definition referred to,
698 allowing this direct connection. This connection provides the use-def
699 information in LLVM.<p>
701 <!-- _______________________________________________________________________ -->
702 </ul><h4><a name="m_User"><hr size=0>Important Public Members of
703 the <tt>User</tt> class</h4><ul>
705 The <tt>User</tt> class exposes the operand list in two ways: through an index
706 access interface and through an iterator based interface.<p>
708 <li><tt>Value *getOperand(unsigned i)</tt><br>
709 <tt>unsigned getNumOperands()</tt><p>
711 These two methods expose the operands of the <tt>User</tt> in a convenient form
712 for direct access.<p>
714 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
715 <tt>User::op_const_iterator</tt>
716 <tt>use_iterator op_begin()</tt>
717 - Get an iterator to the start of the operand list.<br>
718 <tt>use_iterator op_end()</tt>
719 - Get an iterator to the end of the operand list.<p>
721 Together, these methods make up the iterator based interface to the operands of
726 <!-- ======================================================================= -->
727 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
728 <tr><td> </td><td width="100%">
729 <font color="#EEEEFF" face="Georgia,Palatino"><b>
730 <a name="Instruction">The <tt>Instruction</tt> class</a>
731 </b></font></td></tr></table><ul>
734 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
735 doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
736 Superclasses: <a href="#User"><tt>User</tt></a>, <a
737 href="#Value"><tt>Value</tt></a><p>
739 The <tt>Instruction</tt> class is the common base class for all LLVM
740 instructions. It provides only a few methods, but is a very commonly used
741 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
742 opcode (instruction type) and the parent <a
743 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
744 into. To represent a specific type of instruction, one of many subclasses of
745 <tt>Instruction</tt> are used.<p>
747 Because the <tt>Instruction</tt> class subclasses the <a
748 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
749 way as for other <a href="#User"><tt>User</tt></a>s (with the
750 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
751 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
754 <!-- _______________________________________________________________________ -->
755 </ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
756 the <tt>Instruction</tt> class</h4><ul>
758 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
760 Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
761 <tt>Instruction</tt> is embedded into.<p>
763 <li><tt>bool hasSideEffects()</tt><p>
765 Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
766 <tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
768 <li><tt>unsigned getOpcode()</tt><p>
770 Returns the opcode for the <tt>Instruction</tt>.<p>
774 \subsection{Subclasses of Instruction :}
776 <li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
778 <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.
780 <li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
782 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
783 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
784 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
787 <li>PHINode : This represents the PHI instructions in the SSA form.
789 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
790 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
791 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
792 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
793 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
794 Add an incoming value to the end of the PHI list
795 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
796 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
798 <li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
799 <li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
801 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
803 <li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
805 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
807 <li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
809 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
810 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
811 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
819 <!-- ======================================================================= -->
820 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
821 <tr><td> </td><td width="100%">
822 <font color="#EEEEFF" face="Georgia,Palatino"><b>
823 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
824 </b></font></td></tr></table><ul>
827 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
828 doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
829 Superclass: <a href="#Value"><tt>Value</tt></a><p>
832 This class represents a single entry multiple exit section of the code, commonly
833 known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
834 maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
835 the body of the block. Matching the language definition, the last element of
836 this list of instructions is always a terminator instruction (a subclass of the
837 <a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
839 In addition to tracking the list of instructions that make up the block, the
840 <tt>BasicBlock</tt> class also keeps track of the <a
841 href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
843 Note that <tt>BasicBlock</tt>s themselves are <a
844 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
845 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
849 <!-- _______________________________________________________________________ -->
850 </ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
851 the <tt>BasicBlock</tt> class</h4><ul>
853 <li><tt>BasicBlock(const std::string &Name = "", <a
854 href="#Function">Function</a> *Parent = 0)</tt><p>
856 The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
857 insertion into a function. The constructor simply takes a name for the new
858 block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
859 into. If the <tt>Parent</tt> parameter is specified, the new
860 <tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
861 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
862 manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
864 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
865 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
866 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
867 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
869 These methods and typedefs are forwarding functions that have the same semantics
870 as the standard library methods of the same names. These methods expose the
871 underlying instruction list of a basic block in a way that is easy to
872 manipulate. To get the full complement of container operations (including
873 operations to update the list), you must use the <tt>getInstList()</tt>
876 <li><tt>BasicBlock::InstListType &getInstList()</tt><p>
878 This method is used to get access to the underlying container that actually
879 holds the Instructions. This method must be used when there isn't a forwarding
880 function in the <tt>BasicBlock</tt> class for the operation that you would like
881 to perform. Because there are no forwarding functions for "updating"
882 operations, you need to use this if you want to update the contents of a
883 <tt>BasicBlock</tt>.<p>
885 <li><tt><A href="#Function">Function</a> *getParent()</tt><p>
887 Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
888 embedded into, or a null pointer if it is homeless.<p>
890 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
892 Returns a pointer to the terminator instruction that appears at the end of the
893 <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
894 instruction in the block is not a terminator, then a null pointer is
898 <!-- ======================================================================= -->
899 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
900 <tr><td> </td><td width="100%">
901 <font color="#EEEEFF" face="Georgia,Palatino"><b>
902 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
903 </b></font></td></tr></table><ul>
906 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
907 doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
908 Superclasses: <a href="#User"><tt>User</tt></a>, <a
909 href="#Value"><tt>Value</tt></a><p>
911 Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
912 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
913 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
914 Because they are visible at global scope, they are also subject to linking with
915 other globals defined in different translation units. To control the linking
916 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
917 <tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
919 If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
920 <tt>static</tt> in C), it is not visible to code outside the current translation
921 unit, and does not participate in linking. If it has external linkage, it is
922 visible to external code, and does participate in linking. In addition to
923 linkage information, <tt>GlobalValue</tt>s keep track of which <a
924 href="#Module"><tt>Module</tt></a> they are currently part of.<p>
926 Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
927 their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
928 always a pointer to its contents. This is explained in the LLVM Language
932 <!-- _______________________________________________________________________ -->
933 </ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
934 the <tt>GlobalValue</tt> class</h4><ul>
936 <li><tt>bool hasInternalLinkage() const</tt><br>
937 <tt>bool hasExternalLinkage() const</tt><br>
938 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
940 These methods manipulate the linkage characteristics of the
941 <tt>GlobalValue</tt>.<p>
943 <li><tt><a href="#Module">Module</a> *getParent()</tt><p>
945 This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
946 currently embedded into.<p>
950 <!-- ======================================================================= -->
951 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
952 <tr><td> </td><td width="100%">
953 <font color="#EEEEFF" face="Georgia,Palatino"><b>
954 <a name="Function">The <tt>Function</tt> class</a>
955 </b></font></td></tr></table><ul>
958 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
959 doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
960 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
961 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
963 The <tt>Function</tt> class represents a single procedure in LLVM. It is
964 actually one of the more complex classes in the LLVM heirarchy because it must
965 keep track of a large amount of data. The <tt>Function</tt> class keeps track
966 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
967 href="#Argument"><tt>Argument</tt></a>s, and a <a
968 href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
970 The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
971 used part of <tt>Function</tt> objects. The list imposes an implicit ordering
972 of the blocks in the function, which indicate how the code will be layed out by
973 the backend. Additionally, the first <a
974 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
975 <tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
976 block. There are no implicit exit nodes, and in fact there may be multiple exit
977 nodes from a single <tt>Function</tt>. If the <a
978 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
979 the <tt>Function</tt> is actually a function declaration: the actual body of the
980 function hasn't been linked in yet.<p>
982 In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
983 <tt>Function</tt> class also keeps track of the list of formal <a
984 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
985 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
986 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
987 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
989 The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
990 feature that is only used when you have to look up a value by name. Aside from
991 that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
992 make sure that there are not conflicts between the names of <a
993 href="#Instruction"><tt>Instruction</tt></a>s, <a
994 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
995 href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
998 <!-- _______________________________________________________________________ -->
999 </ul><h4><a name="m_Function"><hr size=0>Important Public Members of
1000 the <tt>Function</tt> class</h4><ul>
1002 <li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
1004 Constructor used when you need to create new <tt>Function</tt>s to add the the
1005 program. The constructor must specify the type of the function to create and
1006 whether or not it should start out with internal or external linkage.<p>
1008 <li><tt>bool isExternal()</tt><p>
1010 Return whether or not the <tt>Function</tt> has a body defined. If the function
1011 is "external", it does not have a body, and thus must be resolved by linking
1012 with a function defined in a different translation unit.<p>
1015 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
1016 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
1017 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1018 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1020 These are forwarding methods that make it easy to access the contents of a
1021 <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
1024 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
1026 Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
1027 neccesary to use when you need to update the list or perform a complex action
1028 that doesn't have a forwarding method.<p>
1031 <li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
1032 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
1033 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
1034 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
1036 These are forwarding methods that make it easy to access the contents of a
1037 <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
1039 <li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
1041 Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
1042 neccesary to use when you need to update the list or perform a complex action
1043 that doesn't have a forwarding method.<p>
1047 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
1049 Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
1050 function. Because the entry block for the function is always the first block,
1051 this returns the first block of the <tt>Function</tt>.<p>
1053 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
1054 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
1056 This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
1057 and returns the return type of the function, or the <a
1058 href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
1061 <li><tt>bool hasSymbolTable() const</tt><p>
1063 Return true if the <tt>Function</tt> has a symbol table allocated to it and if
1064 there is at least one entry in it.<p>
1066 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1068 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1069 <tt>Function</tt> or a null pointer if one has not been allocated (because there
1070 are no named values in the function).<p>
1072 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
1074 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1075 <tt>Function</tt> or allocate a new <a
1076 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
1077 should only be used when adding elements to the <a
1078 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
1079 not left laying around.<p>
1083 <!-- ======================================================================= -->
1084 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1085 <tr><td> </td><td width="100%">
1086 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1087 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
1088 </b></font></td></tr></table><ul>
1091 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
1092 doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
1093 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
1094 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
1096 Global variables are represented with the (suprise suprise)
1097 <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
1098 also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
1099 are always referenced by their address (global values must live in memory, so
1100 their "name" refers to their address). Global variables may have an initial
1101 value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
1102 have an initializer, they may be marked as "constant" themselves (indicating
1103 that their contents never change at runtime).<p>
1106 <!-- _______________________________________________________________________ -->
1107 </ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
1108 <tt>GlobalVariable</tt> class</h4><ul>
1110 <li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
1111 isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
1112 &Name = "")</tt><p>
1114 Create a new global variable of the specified type. If <tt>isConstant</tt> is
1115 true then the global variable will be marked as unchanging for the program, and
1116 if <tt>isInternal</tt> is true the resultant global variable will have internal
1117 linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
1120 <li><tt>bool isConstant() const</tt><p>
1122 Returns true if this is a global variable is known not to be modified at
1126 <li><tt>bool hasInitializer()</tt><p>
1128 Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
1131 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
1133 Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
1134 this method if there is no initializer.<p>
1137 <!-- ======================================================================= -->
1138 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1139 <tr><td> </td><td width="100%">
1140 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1141 <a name="Module">The <tt>Module</tt> class</a>
1142 </b></font></td></tr></table><ul>
1145 href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
1146 doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
1148 The <tt>Module</tt> class represents the top level structure present in LLVM
1149 programs. An LLVM module is effectively either a translation unit of the
1150 original program or a combination of several translation units merged by the
1151 linker. The <tt>Module</tt> class keeps track of a list of <a
1152 href="#Function"><tt>Function</tt></a>s, a list of <a
1153 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
1154 href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
1155 helpful member functions that try to make common operations easy.<p>
1158 <!-- _______________________________________________________________________ -->
1159 </ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
1160 <tt>Module</tt> class</h4><ul>
1162 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
1163 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
1164 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
1165 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
1167 These are forwarding methods that make it easy to access the contents of a
1168 <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
1171 <li><tt>Module::FunctionListType &getFunctionList()</tt><p>
1173 Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
1174 neccesary to use when you need to update the list or perform a complex action
1175 that doesn't have a forwarding method.<p>
1177 <!-- Global Variable -->
1180 <li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
1181 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
1182 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
1183 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
1185 These are forwarding methods that make it easy to access the contents of a
1186 <tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
1189 <li><tt>Module::GlobalListType &getGlobalList()</tt><p>
1191 Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
1192 This is neccesary to use when you need to update the list or perform a complex
1193 action that doesn't have a forwarding method.<p>
1196 <!-- Symbol table stuff -->
1199 <li><tt>bool hasSymbolTable() const</tt><p>
1201 Return true if the <tt>Module</tt> has a symbol table allocated to it and if
1202 there is at least one entry in it.<p>
1204 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
1206 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1207 <tt>Module</tt> or a null pointer if one has not been allocated (because there
1208 are no named values in the function).<p>
1210 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
1212 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
1213 <tt>Module</tt> or allocate a new <a
1214 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
1215 should only be used when adding elements to the <a
1216 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
1217 not left laying around.<p>
1220 <!-- Convenience methods -->
1223 <li><tt><a href="#Function">Function</a> *getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
1225 Look up the specified function in the <tt>Module</tt> <a
1226 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
1230 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
1231 &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
1233 Look up the specified function in the <tt>Module</tt> <a
1234 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
1235 external declaration for the function and return it.<p>
1238 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
1240 If there is at least one entry in the <a
1241 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
1242 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
1246 <li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
1249 Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
1250 <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
1251 is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
1255 <!-- ======================================================================= -->
1256 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1257 <tr><td> </td><td width="100%">
1258 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1259 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
1260 </b></font></td></tr></table><ul>
1262 Constant represents a base class for different types of constants. It is
1263 subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
1264 ConstantArray etc for representing the various types of Constants.<p>
1267 <!-- _______________________________________________________________________ -->
1268 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1270 <li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
1275 \subsection{Important Subclasses of Constant}
1277 <li>ConstantSInt : This subclass of Constant represents a signed integer constant.
1279 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
1281 <li>ConstantUInt : This class represents an unsigned integer.
1283 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
1285 <li>ConstantFP : This class represents a floating point constant.
1287 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
1289 <li>ConstantBool : This represents a boolean constant.
1291 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
1293 <li>ConstantArray : This represents a constant array.
1295 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1297 <li>ConstantStruct : This represents a constant struct.
1299 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
1301 <li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
1303 <li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
1308 <!-- ======================================================================= -->
1309 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1310 <tr><td> </td><td width="100%">
1311 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1312 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
1313 </b></font></td></tr></table><ul>
1315 Type as noted earlier is also a subclass of a Value class. Any primitive
1316 type (like int, short etc) in LLVM is an instance of Type Class. All
1317 other types are instances of subclasses of type like FunctionType,
1318 ArrayType etc. DerivedType is the interface for all such dervied types
1319 including FunctionType, ArrayType, PointerType, StructType. Types can have
1320 names. They can be recursive (StructType). There exists exactly one instance
1321 of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
1323 <!-- _______________________________________________________________________ -->
1324 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
1326 <li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
1327 <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.
1328 <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.
1329 <li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
1330 <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.
1332 <li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
1333 <li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
1334 <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.
1335 <li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
1336 <li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
1337 <li><tt>const Type * getContainedType (unsigned i) const</tt>:
1338 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.
1339 <li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
1343 \subsection{Derived Types}
1345 <li>SequentialType : This is subclassed by ArrayType and PointerType
1347 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
1349 <li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
1351 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
1353 <li>PointerType : Subclass of SequentialType for pointer types.
1354 <li>StructType : subclass of DerivedTypes for struct types
1355 <li>FunctionType : subclass of DerivedTypes for function types.
1358 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
1359 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
1360 <li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
1361 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
1362 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
1369 <!-- ======================================================================= -->
1370 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
1371 <tr><td> </td><td width="100%">
1372 <font color="#EEEEFF" face="Georgia,Palatino"><b>
1373 <a name="Argument">The <tt>Argument</tt> class</a>
1374 </b></font></td></tr></table><ul>
1376 This subclass of Value defines the interface for incoming formal arguments to a
1377 function. A Function maitanis a list of its formal arguments. An argument has a
1378 pointer to the parent Function.
1383 <!-- *********************************************************************** -->
1385 <!-- *********************************************************************** -->
1388 <address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
1389 <a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
1390 <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
1391 <!-- hhmts start -->
1392 Last modified: Tue Sep 10 10:19:56 CDT 2002
1394 </font></body></html>