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2 <html><head><title>LLVM Programmer's Manual</title></head>
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>The isa<>, cast<> and dyn_cast<> templates
17 <li><a href="#coreclasses">The Core LLVM Class Heirarchy Reference</a>
19 <li><a href="#Value">The <tt>Value</tt> class</a>
21 <li><a href="#User">The <tt>User</tt> class</a>
23 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
28 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
30 <li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a>
31 <li><a href="#Function">The <tt>Function</tt> class</a>
32 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a>
34 <li><a href="#Module">The <tt>Module</tt> class</a>
35 <li><a href="#Constant">The <tt>Constant</tt> class</a>
41 <li><a href="#Type">The <tt>Type</tt> class</a>
42 <li><a href="#Argument">The <tt>Argument</tt> class</a>
44 <li>The <tt>SymbolTable</tt> class
45 <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
47 <li>Creating, inserting, moving and deleting from LLVM lists
49 <li>Important iterator invalidation semantics to be aware of
53 III. Useful things to know about the LLVM source base:
55 III.1 Useful links that introduce the STL
56 III.2 isa<>, cast<>, dyn_cast<>
57 III.3 Makefiles, useful options
58 III.4 How to use opt & analyze to debug stuff
59 III.5 How to write a regression test
60 III.6 DEBUG() and Statistics (-debug & -stats)
61 III.7 The -time-passes option
62 III.8 ... more as needed ...
66 <p><b>Written by <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>
67 and <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
71 <!-- *********************************************************************** -->
72 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
73 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
74 <a name="introduction">Introduction
75 </b></font></td></tr></table><ul>
76 <!-- *********************************************************************** -->
78 This document is meant to hi-light some of the important classes and interfaces
79 available in the LLVM source-base. This manual is not indended to explain what
80 LLVM is, how it works, and what LLVM code looks like. It assumes that you know
81 the basics of LLVM and are interested in writing transformations or otherwise
82 analyzing or manipulating the code.<p>
84 This document should get you oriented so that you can find your way in the
85 continuously growing source code that makes up the LLVM infrastructure. Note
86 that this manual is not intended to serve as a replacement for reading the
87 source code, so if you think there should be a method in one of these classes to
88 do something, but it's not listed, check the source. Links to the <a
89 href="/doxygen/">doxygen</a> sources are provided to make this as easy as
92 The first section of this document describes general information that is useful
93 to know when working in the LLVM infrastructure, and the second describes the
94 Core LLVM classes. In the future this manual will be extended with information
95 describing how to use extension libraries, such as dominator information, CFG
96 traversal routines, and useful utilities like the <tt><a
97 href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
100 <!-- *********************************************************************** -->
101 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
102 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
103 <a name="general">General Information
104 </b></font></td></tr></table><ul>
105 <!-- *********************************************************************** -->
107 This section contains general information that is useful if you are working in
108 the LLVM source-base, but that isn't specific to any particular API.<p>
111 <!-- ======================================================================= -->
112 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
113 <tr><td> </td><td width="100%">
114 <font color="#EEEEFF" face="Georgia,Palatino"><b>
115 <a name="stl">The C++ Standard Template Library</a>
116 </b></font></td></tr></table><ul>
118 LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
119 more than you are used to, or have seen before. Because of this, you might want
120 to do a little background reading in the techniques used and capabilities of the
121 library. There are many good pages that discuss the STL, and several books on
122 the subject that you can get, so it will not be discussed in this document.<p>
124 Here are some useful links:<p>
126 <li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
127 Library reference</a> - an excellent reference for the STL and other parts of
128 the standard C++ library.<br>
130 <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
133 <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
135 href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
138 <li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
143 You are also encouraged to take a look at the <a
144 href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
145 to write maintainable code more than where to put your curly braces.<p>
149 <!-- *********************************************************************** -->
150 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
151 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
152 <a name="coreclasses">The Core LLVM Class Heirarchy Reference
153 </b></font></td></tr></table><ul>
154 <!-- *********************************************************************** -->
156 The Core LLVM classes are the primary means of representing the program being
157 inspected or transformed. The core LLVM classes are defined in header files in
158 the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
162 <!-- ======================================================================= -->
163 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
164 <tr><td> </td><td width="100%">
165 <font color="#EEEEFF" face="Georgia,Palatino"><b>
166 <a name="Value">The <tt>Value</tt> class</a>
167 </b></font></td></tr></table><ul>
169 <tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
170 doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
173 The <tt>Value</tt> class is the most important class in LLVM Source base. It
174 represents a typed value that may be used (among other things) as an operand to
175 an instruction. There are many different types of <tt>Value</tt>s, such as <a
176 href="#Constant"><tt>Constant</tt></a>s, <a
177 href="#Argument"><tt>Argument</tt></a>s, and even <a
178 href="#Instruction"><tt>Instruction</tt></a>s and <a
179 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
181 A particular <tt>Value</tt> may be used many times in the LLVM representation
182 for a program. For example, an incoming argument to a function (represented
183 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
184 every instruction in the function that references the argument. To keep track
185 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
186 href="#User"><tt>User</tt></a>s that is using it (the <a
187 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
188 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
189 def-use information in the program, and is accessable through the <tt>use_</tt>*
190 methods, shown below.<p>
192 Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
193 this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
194 method. <a name="#nameWarning">In addition, all LLVM values can be named. The
195 "name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
198 %<b>foo</b> = add int 1, 2
201 The name of this instruction is "foo". <b>NOTE</b> that the name of any value
202 may be missing (an empty string), so names should <b>ONLY</b> be used for
203 debugging (making the source code easier to read, debugging printouts), they
204 should not be used to keep track of values or map between them. For this
205 purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
208 One important aspect of LLVM is that there is no distinction between an SSA
209 variable and the operation that produces it. Because of this, any reference to
210 the value produced by an instruction (or the value available as an incoming
211 argument, for example) is represented as a direct pointer to the class that
212 represents this value. Although this may take some getting used to, it
213 simplifies the representation and makes it easier to manipulate.<p>
216 <!-- _______________________________________________________________________ -->
217 </ul><h4><a name="m_Value"><hr size=0>Important Public Members of
218 the <tt>Value</tt> class</h4><ul>
220 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
221 <tt>Value::use_const_iterator</tt>
222 - Typedef for const_iterator over the use-list<br>
223 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
224 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
225 <tt>use_iterator use_begin()</tt>
226 - Get an iterator to the start of the use-list.<br>
227 <tt>use_iterator use_end()</tt>
228 - Get an iterator to the end of the use-list.<br>
229 <tt><a href="#User">User</a> *use_back()</tt>
230 - Returns the last element in the list.<p>
232 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>
234 <li><tt><a href="#Type">Type</a> *getType() const</tt><p>
235 This method returns the Type of the Value.
237 <li><tt>bool hasName() const</tt><br>
238 <tt>std::string getName() const</tt><br>
239 <tt>void setName(const std::string &Name)</tt><p>
241 This family of methods is used to access and assign a name to a <tt>Value</tt>,
242 be aware of the <a href="#nameWarning">precaution above</a>.<p>
245 <li><tt>void replaceAllUsesWith(Value *V)</tt><p>
247 This method traverses the use list of a <tt>Value</tt> changing all <a
248 href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
249 instead. For example, if you detect that an instruction always produces a
250 constant value (for example through constant folding), you can replace all uses
251 of the instruction with the constant like this:<p>
254 Inst->replaceAllUsesWith(ConstVal);
259 <!-- ======================================================================= -->
260 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
261 <tr><td> </td><td width="100%">
262 <font color="#EEEEFF" face="Georgia,Palatino"><b>
263 <a name="User">The <tt>User</tt> class</a>
264 </b></font></td></tr></table><ul>
266 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
267 doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
268 Superclass: <a href="#Value"><tt>Value</tt></a><p>
271 The <tt>User</tt> class is the common base class of all LLVM nodes that may
272 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
273 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
274 referring to. The <tt>User</tt> class itself is a subclass of
277 The operands of a <tt>User</tt> point directly to the LLVM <a
278 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
279 Single Assignment (SSA) form, there can only be one definition referred to,
280 allowing this direct connection. This connection provides the use-def
281 information in LLVM.<p>
283 <!-- _______________________________________________________________________ -->
284 </ul><h4><a name="m_User"><hr size=0>Important Public Members of
285 the <tt>User</tt> class</h4><ul>
287 The <tt>User</tt> class exposes the operand list in two ways: through an index
288 access interface and through an iterator based interface.<p>
290 <li><tt>Value *getOperand(unsigned i)</tt><br>
291 <tt>unsigned getNumOperands()</tt><p>
293 These two methods expose the operands of the <tt>User</tt> in a convenient form
294 for direct access.<p>
296 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
297 <tt>User::op_const_iterator</tt>
298 <tt>use_iterator op_begin()</tt>
299 - Get an iterator to the start of the operand list.<br>
300 <tt>use_iterator op_end()</tt>
301 - Get an iterator to the end of the operand list.<p>
303 Together, these methods make up the iterator based interface to the operands of
308 <!-- ======================================================================= -->
309 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
310 <tr><td> </td><td width="100%">
311 <font color="#EEEEFF" face="Georgia,Palatino"><b>
312 <a name="Instruction">The <tt>Instruction</tt> class</a>
313 </b></font></td></tr></table><ul>
316 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
317 doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
318 Superclasses: <a href="#User"><tt>User</tt></a>, <a
319 href="#Value"><tt>Value</tt></a><p>
321 The <tt>Instruction</tt> class is the common base class for all LLVM
322 instructions. It provides only a few methods, but is a very commonly used
323 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
324 opcode (instruction type) and the parent <a
325 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
326 into. To represent a specific type of instruction, one of many subclasses of
327 <tt>Instruction</tt> are used.<p>
329 Because the <tt>Instruction</tt> class subclasses the <a
330 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
331 way as for other <a href="#User"><tt>User</tt></a>s (with the
332 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
333 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
336 <!-- _______________________________________________________________________ -->
337 </ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
338 the <tt>Instruction</tt> class</h4><ul>
340 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
342 Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
343 <tt>Instruction</tt> is embedded into.<p>
345 <li><tt>bool hasSideEffects()</tt><p>
347 Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
348 <tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
350 <li><tt>unsigned getOpcode()</tt><p>
352 Returns the opcode for the <tt>Instruction</tt>.<p>
356 \subsection{Subclasses of Instruction :}
358 <li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
360 <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 <li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
364 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
365 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
366 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
369 <li>PHINode : This represents the PHI instructions in the SSA form.
371 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
372 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
373 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
374 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
375 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
376 Add an incoming value to the end of the PHI list
377 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
378 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
380 <li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
381 <li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
383 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
385 <li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
387 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
389 <li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
391 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
392 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
393 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
401 <!-- ======================================================================= -->
402 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
403 <tr><td> </td><td width="100%">
404 <font color="#EEEEFF" face="Georgia,Palatino"><b>
405 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
406 </b></font></td></tr></table><ul>
409 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
410 doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
411 Superclass: <a href="#Value"><tt>Value</tt></a><p>
414 This class represents a single entry multiple exit section of the code, commonly
415 known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
416 maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
417 the body of the block. Matching the language definition, the last element of
418 this list of instructions is always a terminator instruction (a subclass of the
419 <a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
421 In addition to tracking the list of instructions that make up the block, the
422 <tt>BasicBlock</tt> class also keeps track of the <a
423 href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
425 Note that <tt>BasicBlock</tt>s themselves are <a
426 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
427 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
431 <!-- _______________________________________________________________________ -->
432 </ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
433 the <tt>BasicBlock</tt> class</h4><ul>
435 <li><tt>BasicBlock(const std::string &Name = "", <a
436 href="#Function">Function</a> *Parent = 0)</tt><p>
438 The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
439 insertion into a function. The constructor simply takes a name for the new
440 block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
441 into. If the <tt>Parent</tt> parameter is specified, the new
442 <tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
443 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
444 manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
446 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
447 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
448 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
449 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
451 These methods and typedefs are forwarding functions that have the same semantics
452 as the standard library methods of the same names. These methods expose the
453 underlying instruction list of a basic block in a way that is easy to
454 manipulate. To get the full complement of container operations (including
455 operations to update the list), you must use the <tt>getInstList()</tt>
458 <li><tt>BasicBlock::InstListType &getInstList()</tt><p>
460 This method is used to get access to the underlying container that actually
461 holds the Instructions. This method must be used when there isn't a forwarding
462 function in the <tt>BasicBlock</tt> class for the operation that you would like
463 to perform. Because there are no forwarding functions for "updating"
464 operations, you need to use this if you want to update the contents of a
465 <tt>BasicBlock</tt>.<p>
467 <li><tt><A href="#Function">Function</a> *getParent()</tt><p>
469 Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
470 embedded into, or a null pointer if it is homeless.<p>
472 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
474 Returns a pointer to the terminator instruction that appears at the end of the
475 <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
476 instruction in the block is not a terminator, then a null pointer is
480 <!-- ======================================================================= -->
481 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
482 <tr><td> </td><td width="100%">
483 <font color="#EEEEFF" face="Georgia,Palatino"><b>
484 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
485 </b></font></td></tr></table><ul>
488 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
489 doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
490 Superclasses: <a href="#User"><tt>User</tt></a>, <a
491 href="#Value"><tt>Value</tt></a><p>
493 Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
494 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
495 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
496 Because they are visible at global scope, they are also subject to linking with
497 other globals defined in different translation units. To control the linking
498 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
499 <tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
501 If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
502 <tt>static</tt> in C), it is not visible to code outside the current translation
503 unit, and does not participate in linking. If it has external linkage, it is
504 visible to external code, and does participate in linking. In addition to
505 linkage information, <tt>GlobalValue</tt>s keep track of which <a
506 href="#Module"><tt>Module</tt></a> they are currently part of.<p>
508 Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
509 their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
510 always a pointer to its contents. This is explained in the LLVM Language
514 <!-- _______________________________________________________________________ -->
515 </ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
516 the <tt>GlobalValue</tt> class</h4><ul>
518 <li><tt>bool hasInternalLinkage() const</tt><br>
519 <tt>bool hasExternalLinkage() const</tt><br>
520 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
522 These methods manipulate the linkage characteristics of the
523 <tt>GlobalValue</tt>.<p>
525 <li><tt><a href="#Module">Module</a> *getParent()</tt><p>
527 This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
528 currently embedded into.<p>
532 <!-- ======================================================================= -->
533 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
534 <tr><td> </td><td width="100%">
535 <font color="#EEEEFF" face="Georgia,Palatino"><b>
536 <a name="Function">The <tt>Function</tt> class</a>
537 </b></font></td></tr></table><ul>
540 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
541 doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
542 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
543 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
545 The <tt>Function</tt> class represents a single procedure in LLVM. It is
546 actually one of the more complex classes in the LLVM heirarchy because it must
547 keep track of a large amount of data. The <tt>Function</tt> class keeps track
548 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
549 href="#Argument"><tt>Argument</tt></a>s, and a <a
550 href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
552 The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
553 used part of <tt>Function</tt> objects. The list imposes an implicit ordering
554 of the blocks in the function, which indicate how the code will be layed out by
555 the backend. Additionally, the first <a
556 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
557 <tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
558 block. There are no implicit exit nodes, and in fact there may be multiple exit
559 nodes from a single <tt>Function</tt>. If the <a
560 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
561 the <tt>Function</tt> is actually a function declaration: the actual body of the
562 function hasn't been linked in yet.<p>
564 In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
565 <tt>Function</tt> class also keeps track of the list of formal <a
566 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
567 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
568 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
569 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
571 The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
572 feature that is only used when you have to look up a value by name. Aside from
573 that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
574 make sure that there are not conflicts between the names of <a
575 href="#Instruction"><tt>Instruction</tt></a>s, <a
576 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
577 href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
580 <!-- _______________________________________________________________________ -->
581 </ul><h4><a name="m_Function"><hr size=0>Important Public Members of
582 the <tt>Function</tt> class</h4><ul>
584 <li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
586 Constructor used when you need to create new <tt>Function</tt>s to add the the
587 program. The constructor must specify the type of the function to create and
588 whether or not it should start out with internal or external linkage.<p>
590 <li><tt>bool isExternal()</tt><p>
592 Return whether or not the <tt>Function</tt> has a body defined. If the function
593 is "external", it does not have a body, and thus must be resolved by linking
594 with a function defined in a different translation unit.<p>
597 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
598 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
599 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
600 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
602 These are forwarding methods that make it easy to access the contents of a
603 <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
606 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
608 Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
609 neccesary to use when you need to update the list or perform a complex action
610 that doesn't have a forwarding method.<p>
613 <li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
614 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
615 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
616 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
618 These are forwarding methods that make it easy to access the contents of a
619 <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
621 <li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
623 Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
624 neccesary to use when you need to update the list or perform a complex action
625 that doesn't have a forwarding method.<p>
629 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
631 Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
632 function. Because the entry block for the function is always the first block,
633 this returns the first block of the <tt>Function</tt>.<p>
635 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
636 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
638 This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
639 and returns the return type of the function, or the <a
640 href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
643 <li><tt>bool hasSymbolTable() const</tt><p>
645 Return true if the <tt>Function</tt> has a symbol table allocated to it and if
646 there is at least one entry in it.<p>
648 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
650 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
651 <tt>Function</tt> or a null pointer if one has not been allocated (because there
652 are no named values in the function).<p>
654 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
656 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
657 <tt>Function</tt> or allocate a new <a
658 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
659 should only be used when adding elements to the <a
660 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
661 not left laying around.<p>
665 <!-- ======================================================================= -->
666 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
667 <tr><td> </td><td width="100%">
668 <font color="#EEEEFF" face="Georgia,Palatino"><b>
669 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
670 </b></font></td></tr></table><ul>
673 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
674 doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
675 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
676 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
678 Global variables are represented with the (suprise suprise)
679 <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
680 also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
681 are always referenced by their address (global values must live in memory, so
682 their "name" refers to their address). Global variables may have an initial
683 value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
684 have an initializer, they may be marked as "constant" themselves (indicating
685 that their contents never change at runtime).<p>
688 <!-- _______________________________________________________________________ -->
689 </ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
690 <tt>GlobalVariable</tt> class</h4><ul>
692 <li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
693 isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
694 &Name = "")</tt><p>
696 Create a new global variable of the specified type. If <tt>isConstant</tt> is
697 true then the global variable will be marked as unchanging for the program, and
698 if <tt>isInternal</tt> is true the resultant global variable will have internal
699 linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
702 <li><tt>bool isConstant() const</tt><p>
704 Returns true if this is a global variable is known not to be modified at
708 <li><tt>bool hasInitializer()</tt><p>
710 Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
713 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
715 Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
716 this method if there is no initializer.<p>
719 <!-- ======================================================================= -->
720 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
721 <tr><td> </td><td width="100%">
722 <font color="#EEEEFF" face="Georgia,Palatino"><b>
723 <a name="Module">The <tt>Module</tt> class</a>
724 </b></font></td></tr></table><ul>
727 href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
728 doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
730 The <tt>Module</tt> class represents the top level structure present in LLVM
731 programs. An LLVM module is effectively either a translation unit of the
732 original program or a combination of several translation units merged by the
733 linker. The <tt>Module</tt> class keeps track of a list of <a
734 href="#Function"><tt>Function</tt></a>s, a list of <a
735 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
736 href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
737 helpful member functions that try to make common operations easy.<p>
740 <!-- _______________________________________________________________________ -->
741 </ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
742 <tt>Module</tt> class</h4><ul>
744 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
745 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
746 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
747 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
749 These are forwarding methods that make it easy to access the contents of a
750 <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
753 <li><tt>Module::FunctionListType &getFunctionList()</tt><p>
755 Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
756 neccesary to use when you need to update the list or perform a complex action
757 that doesn't have a forwarding method.<p>
759 <!-- Global Variable -->
762 <li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
763 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
764 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
765 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
767 These are forwarding methods that make it easy to access the contents of a
768 <tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
771 <li><tt>Module::GlobalListType &getGlobalList()</tt><p>
773 Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
774 This is neccesary to use when you need to update the list or perform a complex
775 action that doesn't have a forwarding method.<p>
778 <!-- Symbol table stuff -->
781 <li><tt>bool hasSymbolTable() const</tt><p>
783 Return true if the <tt>Module</tt> has a symbol table allocated to it and if
784 there is at least one entry in it.<p>
786 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
788 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
789 <tt>Module</tt> or a null pointer if one has not been allocated (because there
790 are no named values in the function).<p>
792 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
794 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
795 <tt>Module</tt> or allocate a new <a
796 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
797 should only be used when adding elements to the <a
798 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
799 not left laying around.<p>
802 <!-- Convenience methods -->
805 <li><tt><a href="#Function">Function</a> *getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
807 Look up the specified function in the <tt>Module</tt> <a
808 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
812 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
813 &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
815 Look up the specified function in the <tt>Module</tt> <a
816 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
817 external declaration for the function and return it.<p>
820 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
822 If there is at least one entry in the <a
823 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
824 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
828 <li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
831 Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
832 <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
833 is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
837 <!-- ======================================================================= -->
838 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
839 <tr><td> </td><td width="100%">
840 <font color="#EEEEFF" face="Georgia,Palatino"><b>
841 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
842 </b></font></td></tr></table><ul>
844 Constant represents a base class for different types of constants. It is
845 subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
846 ConstantArray etc for representing the various types of Constants.<p>
849 <!-- _______________________________________________________________________ -->
850 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
852 <li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
857 \subsection{Important Subclasses of Constant}
859 <li>ConstantSInt : This subclass of Constant represents a signed integer constant.
861 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
863 <li>ConstantUInt : This class represents an unsigned integer.
865 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
867 <li>ConstantFP : This class represents a floating point constant.
869 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
871 <li>ConstantBool : This represents a boolean constant.
873 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
875 <li>ConstantArray : This represents a constant array.
877 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
879 <li>ConstantStruct : This represents a constant struct.
881 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
883 <li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
885 <li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
890 <!-- ======================================================================= -->
891 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
892 <tr><td> </td><td width="100%">
893 <font color="#EEEEFF" face="Georgia,Palatino"><b>
894 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
895 </b></font></td></tr></table><ul>
897 Type as noted earlier is also a subclass of a Value class. Any primitive
898 type (like int, short etc) in LLVM is an instance of Type Class. All
899 other types are instances of subclasses of type like FunctionType,
900 ArrayType etc. DerivedType is the interface for all such dervied types
901 including FunctionType, ArrayType, PointerType, StructType. Types can have
902 names. They can be recursive (StructType). There exists exactly one instance
903 of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
905 <!-- _______________________________________________________________________ -->
906 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
908 <li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
909 <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.
910 <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.
911 <li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
912 <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.
914 <li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
915 <li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
916 <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.
917 <li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
918 <li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
919 <li><tt>const Type * getContainedType (unsigned i) const</tt>:
920 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.
921 <li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
925 \subsection{Derived Types}
927 <li>SequentialType : This is subclassed by ArrayType and PointerType
929 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
931 <li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
933 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
935 <li>PointerType : Subclass of SequentialType for pointer types.
936 <li>StructType : subclass of DerivedTypes for struct types
937 <li>FunctionType : subclass of DerivedTypes for function types.
940 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
941 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
942 <li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
943 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
944 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
951 <!-- ======================================================================= -->
952 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
953 <tr><td> </td><td width="100%">
954 <font color="#EEEEFF" face="Georgia,Palatino"><b>
955 <a name="Argument">The <tt>Argument</tt> class</a>
956 </b></font></td></tr></table><ul>
958 This subclass of Value defines the interface for incoming formal arguments to a
959 function. A Function maitanis a list of its formal arguments. An argument has a
960 pointer to the parent Function.
965 <!-- *********************************************************************** -->
967 <!-- *********************************************************************** -->
970 <address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
971 <a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
972 <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
974 Last modified: Fri Sep 6 11:21:49 CDT 2002
976 </font></body></html>