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2<html><head><title>LLVM Programmer's Manual</title></head>
3
4<body bgcolor=white>
5
6
7<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
8<tr><td>&nbsp; <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM Programmer's Manual</b></font></td>
9</tr></table>
10
11<ol>
12 <li><a href="#introduction">Introduction</a>
13 <li><a href="#general">General Information</a>
14 <ul>
15 <li><a href="#stl">The C++ Standard Template Library</a>
16 <li>The isa&lt;&gt;, cast&lt;&gt; and dyn_cast&lt;&gt; templates
17 </ul>
18 <li><a href="#coreclasses">The Core LLVM Class Heirarchy</a>
19 <ul>
20 <li><a href="#Value">The <tt>Value</tt> class</a>
21 <ul>
22 <li><a href="#User">The <tt>User</tt> class</a>
23 <ul>
24 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
25 <ul>
26 <li>
27 <li>
28 </ul>
29 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
30 <ul>
31 <li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a>
32 <li><a href="#Function">The <tt>Function</tt> class</a>
33 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a>
34 </ul>
35 <li><a href="#Module">The <tt>Module</tt> class</a>
36 <li><a href="#Constant">The <tt>Constant</tt> class</a>
37 <ul>
38 <li>
39 <li>
40 </ul>
41 </ul>
42 <li><a href="#Type">The <tt>Type</tt> class</a>
43 <li><a href="#Argument">The <tt>Argument</tt> class</a>
44 </ul>
45 <li>The <tt>SymbolTable</tt> class
46 <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
47 <ul>
48 <li>Creating, inserting, moving and deleting from LLVM lists
49 </ul>
50 <li>Important iterator invalidation semantics to be aware of
51 </ul>
52
53<!--
54III. Useful things to know about the LLVM source base:
55
56III.1 Useful links that introduce the STL
57III.2 isa<>, cast<>, dyn_cast<>
58III.3 Makefiles, useful options
59III.4 How to use opt & analyze to debug stuff
60III.5 How to write a regression test
61III.6 DEBUG() and Statistics (-debug & -stats)
62III.7 The -time-passes option
63III.8 ... more as needed ...
64
65-->
66
67 <p><b>Written by <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>
68 and <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
69</ol>
70
71
72<!-- *********************************************************************** -->
73<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
74<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
75<a name="introduction">Introduction
76</b></font></td></tr></table><ul>
77<!-- *********************************************************************** -->
78
79This document is meant to hi-light some of the important classes and interfaces
80available in the LLVM source-base. This manual is not indended to explain what
81LLVM is, how it works, and what LLVM code looks like. It assumes that you know
82the basics of LLVM and are interested in writing transformations or otherwise
83analyzing or manipulating the code.<p>
84
85This document should get you oriented so that you can find your way in the
86continuously growing source code that makes up the LLVM infrastructure. Note
87that this manual is not intended to serve as a replacement for reading the
88source code, so if you think there should be a method in one of these classes to
89do something, but it's not listed, check the source. Links to the <a
90href="/doxygen/">doxygen</a> sources are provided to make this as easy as
91possible.<p>
92
93The first section of this document describes general information that is useful
94to know when working in the LLVM infrastructure, and the second describes the
95Core LLVM classes. In the future this manual will be extended with information
96describing how to use extension libraries, such as dominator information, CFG
97traversal routines, and useful utilities like the <tt><a
98href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
99
100
101<!-- *********************************************************************** -->
102</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
103<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
104<a name="general">General Information
105</b></font></td></tr></table><ul>
106<!-- *********************************************************************** -->
107
108This section contains general information that is useful if you are working in
109the LLVM source-base, but that isn't specific to any particular API.<p>
110
111
112<!-- ======================================================================= -->
113</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
114<tr><td>&nbsp;</td><td width="100%">&nbsp;
115<font color="#EEEEFF" face="Georgia,Palatino"><b>
116<a name="stl">The C++ Standard Template Library</a>
117</b></font></td></tr></table><ul>
118
119LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
120more than you are used to, or have seen before. Because of this, you might want
121to do a little background reading in the techniques used and capabilities of the
122library. There are many good pages that discuss the STL, and several books on
123the subject that you can get, so it will not be discussed in this document.<p>
124
125Here are some useful links:<p>
126<ol>
127<li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
128Library reference</a> - an excellent reference for the STL and other parts of
129the standard C++ library.<br>
130
131<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
132Questions</a>
133
134<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
135Contains a useful <a
136href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
137STL</a>.
138
139<li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
140Page</a>
141
142</ol><p>
143
144You are also encouraged to take a look at the <a
145href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
146to write maintainable code more than where to put your curly braces.<p>
147
148
149
150<!-- *********************************************************************** -->
151</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
152<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
153<a name="coreclasses">The Core LLVM Class Heirarchy
154</b></font></td></tr></table><ul>
155<!-- *********************************************************************** -->
156
157The Core LLVM classes are the primary means of representing the program being
158inspected or transformed. The core LLVM classes are defined in header files in
159the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
160directory.<p>
161
162
163<!-- ======================================================================= -->
164</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
165<tr><td>&nbsp;</td><td width="100%">&nbsp;
166<font color="#EEEEFF" face="Georgia,Palatino"><b>
167<a name="Value">The <tt>Value</tt> class</a>
168</b></font></td></tr></table><ul>
169
170<tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
171doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
172
173
174The <tt>Value</tt> class is the most important class in LLVM Source base. It
175represents a typed value that may be used (among other things) as an operand to
176an instruction. There are many different types of <tt>Value</tt>s, such as <a
177href="#Constant"><tt>Constant</tt></a>s, <a
178href="#Argument"><tt>Argument</tt></a>s, and even <a
179href="#Instruction"><tt>Instruction</tt></a>s and <a
180href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
181
182A particular <tt>Value</tt> may be used many times in the LLVM representation
183for a program. For example, an incoming argument to a function (represented
184with an instance of the <a href="#Argument">Argument</a> class) is "used" by
185every instruction in the function that references the argument. To keep track
186of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
187href="#User"><tt>User</tt></a>s that is using it (the <a
188href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
189graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
190def-use information in the program, and is accessable through the <tt>use_</tt>*
191methods, shown below.<p>
192
193Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
194this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
195method. <a name="#nameWarning">In addition, all LLVM values can be named. The
196"name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
197
198<pre>
199 %<b>foo</b> = add int 1, 2
200</pre>
201
202The name of this instruction is "foo". <b>NOTE</b> that the name of any value
203may be missing (an empty string), so names should <b>ONLY</b> be used for
204debugging (making the source code easier to read, debugging printouts), they
205should not be used to keep track of values or map between them. For this
206purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
207instead.<p>
208
209One important aspect of LLVM is that there is no distinction between an SSA
210variable and the operation that produces it. Because of this, any reference to
211the value produced by an instruction (or the value available as an incoming
212argument, for example) is represented as a direct pointer to the class that
213represents this value. Although this may take some getting used to, it
214simplifies the representation and makes it easier to manipulate.<p>
215
216
217<!-- _______________________________________________________________________ -->
218</ul><h4><a name="m_Value"><hr size=0>Important Public Members of
219the <tt>Value</tt> class</h4><ul>
220
221<li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
222 <tt>Value::use_const_iterator</tt>
223 - Typedef for const_iterator over the use-list<br>
224 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
225 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
226 <tt>use_iterator use_begin()</tt>
227 - Get an iterator to the start of the use-list.<br>
228 <tt>use_iterator use_end()</tt>
229 - Get an iterator to the end of the use-list.<br>
230 <tt><a href="#User">User</a> *use_back()</tt>
231 - Returns the last element in the list.<p>
232
233These 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>
234
235<li><tt><a href="#Type">Type</a> *getType() const</tt><p>
236This method returns the Type of the Value.
237
238<li><tt>bool hasName() const</tt><br>
239 <tt>std::string getName() const</tt><br>
240 <tt>void setName(const std::string &amp;Name)</tt><p>
241
242This family of methods is used to access and assign a name to a <tt>Value</tt>,
243be aware of the <a href="#nameWarning">precaution above</a>.<p>
244
245
246<li><tt>void replaceAllUsesWith(Value *V)</tt><p>
247
248This method traverses the use list of a <tt>Value</tt> changing all <a
249href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
250instead. For example, if you detect that an instruction always produces a
251constant value (for example through constant folding), you can replace all uses
252of the instruction with the constant like this:<p>
253
254<pre>
255 Inst-&gt;replaceAllUsesWith(ConstVal);
256</pre><p>
257
258
259
260<!-- ======================================================================= -->
261</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
262<tr><td>&nbsp;</td><td width="100%">&nbsp;
263<font color="#EEEEFF" face="Georgia,Palatino"><b>
264<a name="User">The <tt>User</tt> class</a>
265</b></font></td></tr></table><ul>
266
267<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
268doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
269Superclass: <a href="#Value"><tt>Value</tt></a><p>
270
271
272The <tt>User</tt> class is the common base class of all LLVM nodes that may
273refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
274that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
275referring to. The <tt>User</tt> class itself is a subclass of
276<tt>Value</tt>.<p>
277
278The operands of a <tt>User</tt> point directly to the LLVM <a
279href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
280Single Assignment (SSA) form, there can only be one definition referred to,
281allowing this direct connection. This connection provides the use-def
282information in LLVM.<p>
283
284<!-- _______________________________________________________________________ -->
285</ul><h4><a name="m_User"><hr size=0>Important Public Members of
286the <tt>User</tt> class</h4><ul>
287
288The <tt>User</tt> class exposes the operand list in two ways: through an index
289access interface and through an iterator based interface.<p>
290
291<li><tt>Value *getOperand(unsigned i)</tt><br>
292 <tt>unsigned getNumOperands()</tt><p>
293
294These two methods expose the operands of the <tt>User</tt> in a convenient form
295for direct access.<p>
296
297<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
298 <tt>User::op_const_iterator</tt>
299 <tt>use_iterator op_begin()</tt>
300 - Get an iterator to the start of the operand list.<br>
301 <tt>use_iterator op_end()</tt>
302 - Get an iterator to the end of the operand list.<p>
303
304Together, these methods make up the iterator based interface to the operands of
305a <tt>User</tt>.<p>
306
307
308
309<!-- ======================================================================= -->
310</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
311<tr><td>&nbsp;</td><td width="100%">&nbsp;
312<font color="#EEEEFF" face="Georgia,Palatino"><b>
313<a name="Instruction">The <tt>Instruction</tt> class</a>
314</b></font></td></tr></table><ul>
315
316<tt>#include "<a
317href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
318doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
319Superclasses: <a href="#User"><tt>User</tt></a>, <a
320href="#Value"><tt>Value</tt></a><p>
321
322The <tt>Instruction</tt> class is the common base class for all LLVM
323instructions. It provides only a few methods, but is a very commonly used
324class. The primary data tracked by the <tt>Instruction</tt> class itself is the
325opcode (instruction type) and the parent <a
326href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
327into. To represent a specific type of instruction, one of many subclasses of
328<tt>Instruction</tt> are used.<p>
329
330Because the <tt>Instruction</tt> class subclasses the <a
331href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
332way as for other <a href="#User"><tt>User</tt></a>s (with the
333<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
334<tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
335
336
337<!-- _______________________________________________________________________ -->
338</ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
339the <tt>Instruction</tt> class</h4><ul>
340
341<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
342
343Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
344<tt>Instruction</tt> is embedded into.<p>
345
346<li><tt>bool hasSideEffects()</tt><p>
347
348Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
349<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
350
351<li><tt>unsigned getOpcode()</tt><p>
352
353Returns the opcode for the <tt>Instruction</tt>.<p>
354
355<!--
356
357\subsection{Subclasses of Instruction :}
358\begin{itemize}
359<li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
360 \begin{itemize}
361 <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.
362 \end{itemize}
363<li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
364 \begin{itemize}
365 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
366 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
367 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
368 \end{itemize}
369
370<li>PHINode : This represents the PHI instructions in the SSA form.
371 \begin{itemize}
372 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
373 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
374 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
375 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
376 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
377 Add an incoming value to the end of the PHI list
378 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
379 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
380 \end{itemize}
381<li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
382<li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
383 \begin{itemize}
384 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
385 \end{itemize}
386<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
387 \begin{itemize}
388 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
389 \end{itemize}
390<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
391 \begin{itemize}
392 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
393 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
394 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
395 \end{itemize}
396
397\end{itemize}
398
399-->
400
401
402<!-- ======================================================================= -->
403</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
404<tr><td>&nbsp;</td><td width="100%">&nbsp;
405<font color="#EEEEFF" face="Georgia,Palatino"><b>
406<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
407</b></font></td></tr></table><ul>
408
409<tt>#include "<a
410href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
411doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
412Superclass: <a href="#Value"><tt>Value</tt></a><p>
413
414
415This class represents a single entry multiple exit section of the code, commonly
416known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
417maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
418the body of the block. Matching the language definition, the last element of
419this list of instructions is always a terminator instruction (a subclass of the
420<a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
421
422In addition to tracking the list of instructions that make up the block, the
423<tt>BasicBlock</tt> class also keeps track of the <a
424href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
425
426Note that <tt>BasicBlock</tt>s themselves are <a
427href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
428like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
429<tt>label</tt>.<p>
430
431
432<!-- _______________________________________________________________________ -->
433</ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
434the <tt>BasicBlock</tt> class</h4><ul>
435
436<li><tt>BasicBlock(const std::string &amp;Name = "", <a
437href="#Function">Function</a> *Parent = 0)</tt><p>
438
439The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
440insertion into a function. The constructor simply takes a name for the new
441block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
442into. If the <tt>Parent</tt> parameter is specified, the new
443<tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
444href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
445manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
446
447<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
448 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
449 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
450 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
451
452These methods and typedefs are forwarding functions that have the same semantics
453as the standard library methods of the same names. These methods expose the
454underlying instruction list of a basic block in a way that is easy to
455manipulate. To get the full complement of container operations (including
456operations to update the list), you must use the <tt>getInstList()</tt>
457method.<p>
458
459<li><tt>BasicBlock::InstListType &amp;getInstList()</tt><p>
460
461This method is used to get access to the underlying container that actually
462holds the Instructions. This method must be used when there isn't a forwarding
463function in the <tt>BasicBlock</tt> class for the operation that you would like
464to perform. Because there are no forwarding functions for "updating"
465operations, you need to use this if you want to update the contents of a
466<tt>BasicBlock</tt>.<p>
467
468<li><tt><A href="#Function">Function</a> *getParent()</tt><p>
469
470Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
471embedded into, or a null pointer if it is homeless.<p>
472
473<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
474
475Returns a pointer to the terminator instruction that appears at the end of the
476<tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
477instruction in the block is not a terminator, then a null pointer is
478returned.<p>
479
480
481<!-- ======================================================================= -->
482</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
483<tr><td>&nbsp;</td><td width="100%">&nbsp;
484<font color="#EEEEFF" face="Georgia,Palatino"><b>
485<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
486</b></font></td></tr></table><ul>
487
488<tt>#include "<a
489href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
490doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
491Superclasses: <a href="#User"><tt>User</tt></a>, <a
492href="#Value"><tt>Value</tt></a><p>
493
494Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
495href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
496visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
497Because they are visible at global scope, they are also subject to linking with
498other globals defined in different translation units. To control the linking
499process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
500<tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
501
502If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
503<tt>static</tt> in C), it is not visible to code outside the current translation
504unit, and does not participate in linking. If it has external linkage, it is
505visible to external code, and does participate in linking. In addition to
506linkage information, <tt>GlobalValue</tt>s keep track of which <a
507href="#Module"><tt>Module</tt></a> they are currently part of.<p>
508
509Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
510their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
511always a pointer to its contents. This is explained in the LLVM Language
512Reference Manual.<p>
513
514
515<!-- _______________________________________________________________________ -->
516</ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
517the <tt>GlobalValue</tt> class</h4><ul>
518
519<li><tt>bool hasInternalLinkage() const</tt><br>
520 <tt>bool hasExternalLinkage() const</tt><br>
521 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
522
523These methods manipulate the linkage characteristics of the
524<tt>GlobalValue</tt>.<p>
525
526<li><tt><a href="#Module">Module</a> *getParent()</tt><p>
527
528This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
529currently embedded into.<p>
530
531
532
533<!-- ======================================================================= -->
534</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
535<tr><td>&nbsp;</td><td width="100%">&nbsp;
536<font color="#EEEEFF" face="Georgia,Palatino"><b>
537<a name="Function">The <tt>Function</tt> class</a>
538</b></font></td></tr></table><ul>
539
540<tt>#include "<a
541href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
542doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
543Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
544href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
545
546The <tt>Function</tt> class represents a single procedure in LLVM. It is
547actually one of the more complex classes in the LLVM heirarchy because it must
548keep track of a large amount of data. The <tt>Function</tt> class keeps track
549of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
550href="#Argument"><tt>Argument</tt></a>s, and a <a
551href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
552
553The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
554used part of <tt>Function</tt> objects. The list imposes an implicit ordering
555of the blocks in the function, which indicate how the code will be layed out by
556the backend. Additionally, the first <a
557href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
558<tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
559block. There are no implicit exit nodes, and in fact there may be multiple exit
560nodes from a single <tt>Function</tt>. If the <a
561href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
562the <tt>Function</tt> is actually a function declaration: the actual body of the
563function hasn't been linked in yet.<p>
564
565In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
566<tt>Function</tt> class also keeps track of the list of formal <a
567href="#Argument"><tt>Argument</tt></a>s that the function receives. This
568container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
569nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
570the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
571
572The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
573feature that is only used when you have to look up a value by name. Aside from
574that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
575make sure that there are not conflicts between the names of <a
576href="#Instruction"><tt>Instruction</tt></a>s, <a
577href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
578href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
579
580
581<!-- _______________________________________________________________________ -->
582</ul><h4><a name="m_Function"><hr size=0>Important Public Members of
583the <tt>Function</tt> class</h4><ul>
584
585<li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &amp;N = "")</tt><p>
586
587Constructor used when you need to create new <tt>Function</tt>s to add the the
588program. The constructor must specify the type of the function to create and
589whether or not it should start out with internal or external linkage.<p>
590
591<li><tt>bool isExternal()</tt><p>
592
593Return whether or not the <tt>Function</tt> has a body defined. If the function
594is "external", it does not have a body, and thus must be resolved by linking
595with a function defined in a different translation unit.<p>
596
597
598<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
599 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
600 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
601 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
602
603These are forwarding methods that make it easy to access the contents of a
604<tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
605list.<p>
606
607<li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt><p>
608
609Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
610neccesary to use when you need to update the list or perform a complex action
611that doesn't have a forwarding method.<p>
612
613
614<li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
615 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
616 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
617 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
618
619These are forwarding methods that make it easy to access the contents of a
620<tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
621
622<li><tt>Function::ArgumentListType &amp;getArgumentList()</tt><p>
623
624Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
625neccesary to use when you need to update the list or perform a complex action
626that doesn't have a forwarding method.<p>
627
628
629
630<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
631
632Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
633function. Because the entry block for the function is always the first block,
634this returns the first block of the <tt>Function</tt>.<p>
635
636<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
637 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
638
639This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
640and returns the return type of the function, or the <a
641href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
642
643
644<li><tt>bool hasSymbolTable() const</tt><p>
645
646Return true if the <tt>Function</tt> has a symbol table allocated to it and if
647there is at least one entry in it.<p>
648
649<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
650
651Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
652<tt>Function</tt> or a null pointer if one has not been allocated (because there
653are no named values in the function).<p>
654
655<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
656
657Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
658<tt>Function</tt> or allocate a new <a
659href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
660should only be used when adding elements to the <a
661href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
662not left laying around.<p>
663
664
665
666<!-- ======================================================================= -->
667</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
668<tr><td>&nbsp;</td><td width="100%">&nbsp;
669<font color="#EEEEFF" face="Georgia,Palatino"><b>
670<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
671</b></font></td></tr></table><ul>
672
673<tt>#include "<a
674href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
675doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
676Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
677href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
678
679
680A GlobalVariable is a subclass of GlobalValue and defines the interface to
681global variables in the SSA program. It can have a name and an
682initializer. (initial constant Value)
683
684Can be constant.
685
686
687<!-- _______________________________________________________________________ -->
688</ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of
689the <tt>GlobalVariable</tt> class</h4><ul>
690
691<li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
692isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
693&amp;Name = "")</tt><p>
694
695<li><tt>bool isConstant() const</tt><p>
696
697Returns true if this is a global variable is known not to be modified at
698runtime.<p>
699
700<li><tt>bool hasInitializer()</tt><p>
701
702Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
703
704<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
705
706Returns the intializer<p>
707
708<!-- ======================================================================= -->
709</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
710<tr><td>&nbsp;</td><td width="100%">&nbsp;
711<font color="#EEEEFF" face="Georgia,Palatino"><b>
712<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
713</b></font></td></tr></table><ul>
714
715Constant represents a base class for different types of constants. It is
716subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
717ConstantArray etc for representing the various types of Constants.<p>
718
719
720<!-- _______________________________________________________________________ -->
721</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
722
723<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
724
725
726
727
728\subsection{Important Subclasses of Constant}
729\begin{itemize}
730<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
731 \begin{itemize}
732 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
733 \end{itemize}
734<li>ConstantUInt : This class represents an unsigned integer.
735 \begin{itemize}
736 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
737 \end{itemize}
738<li>ConstantFP : This class represents a floating point constant.
739 \begin{itemize}
740 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
741 \end{itemize}
742<li>ConstantBool : This represents a boolean constant.
743 \begin{itemize}
744 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
745 \end{itemize}
746<li>ConstantArray : This represents a constant array.
747 \begin{itemize}
748 <li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
749 \end{itemize}
750<li>ConstantStruct : This represents a constant struct.
751 \begin{itemize}
752 <li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
753 \end{itemize}
754<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
755 \begin{itemize}
756<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
757 \end{itemize}
758\end{itemize}
759
760
761<!-- ======================================================================= -->
762</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
763<tr><td>&nbsp;</td><td width="100%">&nbsp;
764<font color="#EEEEFF" face="Georgia,Palatino"><b>
765<a name="Type">The <tt>Type</tt> class and Derived Types</a>
766</b></font></td></tr></table><ul>
767
768Type as noted earlier is also a subclass of a Value class. Any primitive
769type (like int, short etc) in LLVM is an instance of Type Class. All
770other types are instances of subclasses of type like FunctionType,
771ArrayType etc. DerivedType is the interface for all such dervied types
772including FunctionType, ArrayType, PointerType, StructType. Types can have
773names. They can be recursive (StructType). There exists exactly one instance
774of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
775
776<!-- _______________________________________________________________________ -->
777</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
778
779<li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
780<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.
781<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.
782<li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
783<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.
784
785<li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
786<li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
787<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.
788<li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
789<li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
790<li><tt>const Type * getContainedType (unsigned i) const</tt>:
791This 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.
792<li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
793
794
795
796\subsection{Derived Types}
797\begin{itemize}
798<li>SequentialType : This is subclassed by ArrayType and PointerType
799 \begin{itemize}
800 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
801 \end{itemize}
802<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
803 \begin{itemize}
804 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
805 \end{itemize}
806<li>PointerType : Subclass of SequentialType for pointer types.
807<li>StructType : subclass of DerivedTypes for struct types
808<li>FunctionType : subclass of DerivedTypes for function types.
809 \begin{itemize}
810
811 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
812 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
813 <li><tt> const ParamTypes &amp;getParamTypes () const</tt>: Returns a vector of parameter types.
814 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
815 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
816 \end{itemize}
817\end{itemize}
818
819
820
821
822<!-- ======================================================================= -->
823</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
824<tr><td>&nbsp;</td><td width="100%">&nbsp;
825<font color="#EEEEFF" face="Georgia,Palatino"><b>
826<a name="Argument">The <tt>Argument</tt> class</a>
827</b></font></td></tr></table><ul>
828
829This subclass of Value defines the interface for incoming formal arguments to a
830function. A Function maitanis a list of its formal arguments. An argument has a
831pointer to the parent Function.
832
833
834
835
836<!-- *********************************************************************** -->
837</ul>
838<!-- *********************************************************************** -->
839
840<hr><font size-1>
841<address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
842<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
843<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
844<!-- hhmts start -->
845Last modified: Thu Sep 5 21:49:34 CDT 2002
846<!-- hhmts end -->
847</font></body></html>