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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="#common">Helpful Hints for Common Operations</a>
13 <li><a href="#general">General Information</a>
15 <li><a href="#stl">The C++ Standard Template Library</a>
16 <li>The isa<>, cast<> and dyn_cast<> templates
18 <li><a href="#coreclasses">The Core LLVM Class Heirarchy Reference</a>
20 <li><a href="#Value">The <tt>Value</tt> class</a>
22 <li><a href="#User">The <tt>User</tt> class</a>
24 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
29 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
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>
35 <li><a href="#Module">The <tt>Module</tt> class</a>
36 <li><a href="#Constant">The <tt>Constant</tt> class</a>
42 <li><a href="#Type">The <tt>Type</tt> class</a>
43 <li><a href="#Argument">The <tt>Argument</tt> class</a>
45 <li>The <tt>SymbolTable</tt> class
46 <li>The <tt>ilist</tt> and <tt>iplist</tt> classes
48 <li>Creating, inserting, moving and deleting from LLVM lists
50 <li>Important iterator invalidation semantics to be aware of
54 III. Useful things to know about the LLVM source base:
56 III.1 Useful links that introduce the STL
57 III.2 isa<>, cast<>, dyn_cast<>
58 III.3 Makefiles, useful options
59 III.4 How to use opt & analyze to debug stuff
60 III.5 How to write a regression test
61 III.6 DEBUG() and Statistics (-debug & -stats)
62 III.7 The -time-passes option
63 III.8 ... more as needed ...
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>
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 <!-- *********************************************************************** -->
79 This document is meant to hi-light some of the important classes and interfaces
80 available in the LLVM source-base. This manual is not indended to explain what
81 LLVM is, how it works, and what LLVM code looks like. It assumes that you know
82 the basics of LLVM and are interested in writing transformations or otherwise
83 analyzing or manipulating the code.<p>
85 This document should get you oriented so that you can find your way in the
86 continuously growing source code that makes up the LLVM infrastructure. Note
87 that this manual is not intended to serve as a replacement for reading the
88 source code, so if you think there should be a method in one of these classes to
89 do something, but it's not listed, check the source. Links to the <a
90 href="/doxygen/">doxygen</a> sources are provided to make this as easy as
93 The first section of this document describes general information that is useful
94 to know when working in the LLVM infrastructure, and the second describes the
95 Core LLVM classes. In the future this manual will be extended with information
96 describing how to use extension libraries, such as dominator information, CFG
97 traversal routines, and useful utilities like the <tt><a
98 href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
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 <!-- *********************************************************************** -->
108 This section contains general information that is useful if you are working in
109 the LLVM source-base, but that isn't specific to any particular API.<p>
112 <!-- ======================================================================= -->
113 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
114 <tr><td> </td><td width="100%">
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>
119 LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
120 more than you are used to, or have seen before. Because of this, you might want
121 to do a little background reading in the techniques used and capabilities of the
122 library. There are many good pages that discuss the STL, and several books on
123 the subject that you can get, so it will not be discussed in this document.<p>
125 Here are some useful links:<p>
127 <li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
128 Library reference</a> - an excellent reference for the STL and other parts of
129 the standard C++ library.<br>
131 <li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
134 <li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
136 href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
139 <li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
144 You are also encouraged to take a look at the <a
145 href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
146 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="common">Helpful Hints for Common Operations
153 </b></font></td></tr></table><ul>
154 <!-- *********************************************************************** -->
158 <!-- *********************************************************************** -->
159 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
160 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
161 <a name="coreclasses">The Core LLVM Class Heirarchy Reference
162 </b></font></td></tr></table><ul>
163 <!-- *********************************************************************** -->
165 The Core LLVM classes are the primary means of representing the program being
166 inspected or transformed. The core LLVM classes are defined in header files in
167 the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
171 <!-- ======================================================================= -->
172 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
173 <tr><td> </td><td width="100%">
174 <font color="#EEEEFF" face="Georgia,Palatino"><b>
175 <a name="Value">The <tt>Value</tt> class</a>
176 </b></font></td></tr></table><ul>
178 <tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
179 doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
182 The <tt>Value</tt> class is the most important class in LLVM Source base. It
183 represents a typed value that may be used (among other things) as an operand to
184 an instruction. There are many different types of <tt>Value</tt>s, such as <a
185 href="#Constant"><tt>Constant</tt></a>s, <a
186 href="#Argument"><tt>Argument</tt></a>s, and even <a
187 href="#Instruction"><tt>Instruction</tt></a>s and <a
188 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
190 A particular <tt>Value</tt> may be used many times in the LLVM representation
191 for a program. For example, an incoming argument to a function (represented
192 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
193 every instruction in the function that references the argument. To keep track
194 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
195 href="#User"><tt>User</tt></a>s that is using it (the <a
196 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
197 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
198 def-use information in the program, and is accessable through the <tt>use_</tt>*
199 methods, shown below.<p>
201 Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
202 this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
203 method. <a name="#nameWarning">In addition, all LLVM values can be named. The
204 "name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
207 %<b>foo</b> = add int 1, 2
210 The name of this instruction is "foo". <b>NOTE</b> that the name of any value
211 may be missing (an empty string), so names should <b>ONLY</b> be used for
212 debugging (making the source code easier to read, debugging printouts), they
213 should not be used to keep track of values or map between them. For this
214 purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
217 One important aspect of LLVM is that there is no distinction between an SSA
218 variable and the operation that produces it. Because of this, any reference to
219 the value produced by an instruction (or the value available as an incoming
220 argument, for example) is represented as a direct pointer to the class that
221 represents this value. Although this may take some getting used to, it
222 simplifies the representation and makes it easier to manipulate.<p>
225 <!-- _______________________________________________________________________ -->
226 </ul><h4><a name="m_Value"><hr size=0>Important Public Members of
227 the <tt>Value</tt> class</h4><ul>
229 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
230 <tt>Value::use_const_iterator</tt>
231 - Typedef for const_iterator over the use-list<br>
232 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
233 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
234 <tt>use_iterator use_begin()</tt>
235 - Get an iterator to the start of the use-list.<br>
236 <tt>use_iterator use_end()</tt>
237 - Get an iterator to the end of the use-list.<br>
238 <tt><a href="#User">User</a> *use_back()</tt>
239 - Returns the last element in the list.<p>
241 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>
243 <li><tt><a href="#Type">Type</a> *getType() const</tt><p>
244 This method returns the Type of the Value.
246 <li><tt>bool hasName() const</tt><br>
247 <tt>std::string getName() const</tt><br>
248 <tt>void setName(const std::string &Name)</tt><p>
250 This family of methods is used to access and assign a name to a <tt>Value</tt>,
251 be aware of the <a href="#nameWarning">precaution above</a>.<p>
254 <li><tt>void replaceAllUsesWith(Value *V)</tt><p>
256 This method traverses the use list of a <tt>Value</tt> changing all <a
257 href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
258 instead. For example, if you detect that an instruction always produces a
259 constant value (for example through constant folding), you can replace all uses
260 of the instruction with the constant like this:<p>
263 Inst->replaceAllUsesWith(ConstVal);
268 <!-- ======================================================================= -->
269 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
270 <tr><td> </td><td width="100%">
271 <font color="#EEEEFF" face="Georgia,Palatino"><b>
272 <a name="User">The <tt>User</tt> class</a>
273 </b></font></td></tr></table><ul>
275 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
276 doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
277 Superclass: <a href="#Value"><tt>Value</tt></a><p>
280 The <tt>User</tt> class is the common base class of all LLVM nodes that may
281 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
282 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
283 referring to. The <tt>User</tt> class itself is a subclass of
286 The operands of a <tt>User</tt> point directly to the LLVM <a
287 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
288 Single Assignment (SSA) form, there can only be one definition referred to,
289 allowing this direct connection. This connection provides the use-def
290 information in LLVM.<p>
292 <!-- _______________________________________________________________________ -->
293 </ul><h4><a name="m_User"><hr size=0>Important Public Members of
294 the <tt>User</tt> class</h4><ul>
296 The <tt>User</tt> class exposes the operand list in two ways: through an index
297 access interface and through an iterator based interface.<p>
299 <li><tt>Value *getOperand(unsigned i)</tt><br>
300 <tt>unsigned getNumOperands()</tt><p>
302 These two methods expose the operands of the <tt>User</tt> in a convenient form
303 for direct access.<p>
305 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
306 <tt>User::op_const_iterator</tt>
307 <tt>use_iterator op_begin()</tt>
308 - Get an iterator to the start of the operand list.<br>
309 <tt>use_iterator op_end()</tt>
310 - Get an iterator to the end of the operand list.<p>
312 Together, these methods make up the iterator based interface to the operands of
317 <!-- ======================================================================= -->
318 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
319 <tr><td> </td><td width="100%">
320 <font color="#EEEEFF" face="Georgia,Palatino"><b>
321 <a name="Instruction">The <tt>Instruction</tt> class</a>
322 </b></font></td></tr></table><ul>
325 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
326 doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
327 Superclasses: <a href="#User"><tt>User</tt></a>, <a
328 href="#Value"><tt>Value</tt></a><p>
330 The <tt>Instruction</tt> class is the common base class for all LLVM
331 instructions. It provides only a few methods, but is a very commonly used
332 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
333 opcode (instruction type) and the parent <a
334 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
335 into. To represent a specific type of instruction, one of many subclasses of
336 <tt>Instruction</tt> are used.<p>
338 Because the <tt>Instruction</tt> class subclasses the <a
339 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
340 way as for other <a href="#User"><tt>User</tt></a>s (with the
341 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
342 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
345 <!-- _______________________________________________________________________ -->
346 </ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
347 the <tt>Instruction</tt> class</h4><ul>
349 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
351 Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
352 <tt>Instruction</tt> is embedded into.<p>
354 <li><tt>bool hasSideEffects()</tt><p>
356 Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
357 <tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
359 <li><tt>unsigned getOpcode()</tt><p>
361 Returns the opcode for the <tt>Instruction</tt>.<p>
365 \subsection{Subclasses of Instruction :}
367 <li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
369 <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.
371 <li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
373 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
374 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
375 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
378 <li>PHINode : This represents the PHI instructions in the SSA form.
380 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
381 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
382 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
383 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
384 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
385 Add an incoming value to the end of the PHI list
386 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
387 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
389 <li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
390 <li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
392 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
394 <li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
396 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
398 <li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
400 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
401 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
402 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
410 <!-- ======================================================================= -->
411 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
412 <tr><td> </td><td width="100%">
413 <font color="#EEEEFF" face="Georgia,Palatino"><b>
414 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
415 </b></font></td></tr></table><ul>
418 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
419 doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
420 Superclass: <a href="#Value"><tt>Value</tt></a><p>
423 This class represents a single entry multiple exit section of the code, commonly
424 known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
425 maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
426 the body of the block. Matching the language definition, the last element of
427 this list of instructions is always a terminator instruction (a subclass of the
428 <a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
430 In addition to tracking the list of instructions that make up the block, the
431 <tt>BasicBlock</tt> class also keeps track of the <a
432 href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
434 Note that <tt>BasicBlock</tt>s themselves are <a
435 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
436 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
440 <!-- _______________________________________________________________________ -->
441 </ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
442 the <tt>BasicBlock</tt> class</h4><ul>
444 <li><tt>BasicBlock(const std::string &Name = "", <a
445 href="#Function">Function</a> *Parent = 0)</tt><p>
447 The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
448 insertion into a function. The constructor simply takes a name for the new
449 block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
450 into. If the <tt>Parent</tt> parameter is specified, the new
451 <tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
452 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
453 manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
455 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
456 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
457 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
458 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
460 These methods and typedefs are forwarding functions that have the same semantics
461 as the standard library methods of the same names. These methods expose the
462 underlying instruction list of a basic block in a way that is easy to
463 manipulate. To get the full complement of container operations (including
464 operations to update the list), you must use the <tt>getInstList()</tt>
467 <li><tt>BasicBlock::InstListType &getInstList()</tt><p>
469 This method is used to get access to the underlying container that actually
470 holds the Instructions. This method must be used when there isn't a forwarding
471 function in the <tt>BasicBlock</tt> class for the operation that you would like
472 to perform. Because there are no forwarding functions for "updating"
473 operations, you need to use this if you want to update the contents of a
474 <tt>BasicBlock</tt>.<p>
476 <li><tt><A href="#Function">Function</a> *getParent()</tt><p>
478 Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
479 embedded into, or a null pointer if it is homeless.<p>
481 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
483 Returns a pointer to the terminator instruction that appears at the end of the
484 <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
485 instruction in the block is not a terminator, then a null pointer is
489 <!-- ======================================================================= -->
490 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
491 <tr><td> </td><td width="100%">
492 <font color="#EEEEFF" face="Georgia,Palatino"><b>
493 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
494 </b></font></td></tr></table><ul>
497 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
498 doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
499 Superclasses: <a href="#User"><tt>User</tt></a>, <a
500 href="#Value"><tt>Value</tt></a><p>
502 Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
503 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
504 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
505 Because they are visible at global scope, they are also subject to linking with
506 other globals defined in different translation units. To control the linking
507 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
508 <tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
510 If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
511 <tt>static</tt> in C), it is not visible to code outside the current translation
512 unit, and does not participate in linking. If it has external linkage, it is
513 visible to external code, and does participate in linking. In addition to
514 linkage information, <tt>GlobalValue</tt>s keep track of which <a
515 href="#Module"><tt>Module</tt></a> they are currently part of.<p>
517 Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
518 their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
519 always a pointer to its contents. This is explained in the LLVM Language
523 <!-- _______________________________________________________________________ -->
524 </ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
525 the <tt>GlobalValue</tt> class</h4><ul>
527 <li><tt>bool hasInternalLinkage() const</tt><br>
528 <tt>bool hasExternalLinkage() const</tt><br>
529 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
531 These methods manipulate the linkage characteristics of the
532 <tt>GlobalValue</tt>.<p>
534 <li><tt><a href="#Module">Module</a> *getParent()</tt><p>
536 This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
537 currently embedded into.<p>
541 <!-- ======================================================================= -->
542 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
543 <tr><td> </td><td width="100%">
544 <font color="#EEEEFF" face="Georgia,Palatino"><b>
545 <a name="Function">The <tt>Function</tt> class</a>
546 </b></font></td></tr></table><ul>
549 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
550 doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
551 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
552 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
554 The <tt>Function</tt> class represents a single procedure in LLVM. It is
555 actually one of the more complex classes in the LLVM heirarchy because it must
556 keep track of a large amount of data. The <tt>Function</tt> class keeps track
557 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
558 href="#Argument"><tt>Argument</tt></a>s, and a <a
559 href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
561 The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
562 used part of <tt>Function</tt> objects. The list imposes an implicit ordering
563 of the blocks in the function, which indicate how the code will be layed out by
564 the backend. Additionally, the first <a
565 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
566 <tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
567 block. There are no implicit exit nodes, and in fact there may be multiple exit
568 nodes from a single <tt>Function</tt>. If the <a
569 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
570 the <tt>Function</tt> is actually a function declaration: the actual body of the
571 function hasn't been linked in yet.<p>
573 In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
574 <tt>Function</tt> class also keeps track of the list of formal <a
575 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
576 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
577 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
578 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
580 The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
581 feature that is only used when you have to look up a value by name. Aside from
582 that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
583 make sure that there are not conflicts between the names of <a
584 href="#Instruction"><tt>Instruction</tt></a>s, <a
585 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
586 href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
589 <!-- _______________________________________________________________________ -->
590 </ul><h4><a name="m_Function"><hr size=0>Important Public Members of
591 the <tt>Function</tt> class</h4><ul>
593 <li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
595 Constructor used when you need to create new <tt>Function</tt>s to add the the
596 program. The constructor must specify the type of the function to create and
597 whether or not it should start out with internal or external linkage.<p>
599 <li><tt>bool isExternal()</tt><p>
601 Return whether or not the <tt>Function</tt> has a body defined. If the function
602 is "external", it does not have a body, and thus must be resolved by linking
603 with a function defined in a different translation unit.<p>
606 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
607 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
608 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
609 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
611 These are forwarding methods that make it easy to access the contents of a
612 <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
615 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
617 Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
618 neccesary to use when you need to update the list or perform a complex action
619 that doesn't have a forwarding method.<p>
622 <li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
623 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
624 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
625 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
627 These are forwarding methods that make it easy to access the contents of a
628 <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
630 <li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
632 Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
633 neccesary to use when you need to update the list or perform a complex action
634 that doesn't have a forwarding method.<p>
638 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
640 Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
641 function. Because the entry block for the function is always the first block,
642 this returns the first block of the <tt>Function</tt>.<p>
644 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
645 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
647 This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
648 and returns the return type of the function, or the <a
649 href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
652 <li><tt>bool hasSymbolTable() const</tt><p>
654 Return true if the <tt>Function</tt> has a symbol table allocated to it and if
655 there is at least one entry in it.<p>
657 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
659 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
660 <tt>Function</tt> or a null pointer if one has not been allocated (because there
661 are no named values in the function).<p>
663 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
665 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
666 <tt>Function</tt> or allocate a new <a
667 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
668 should only be used when adding elements to the <a
669 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
670 not left laying around.<p>
674 <!-- ======================================================================= -->
675 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
676 <tr><td> </td><td width="100%">
677 <font color="#EEEEFF" face="Georgia,Palatino"><b>
678 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
679 </b></font></td></tr></table><ul>
682 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
683 doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
684 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
685 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
687 Global variables are represented with the (suprise suprise)
688 <tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
689 also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
690 are always referenced by their address (global values must live in memory, so
691 their "name" refers to their address). Global variables may have an initial
692 value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
693 have an initializer, they may be marked as "constant" themselves (indicating
694 that their contents never change at runtime).<p>
697 <!-- _______________________________________________________________________ -->
698 </ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
699 <tt>GlobalVariable</tt> class</h4><ul>
701 <li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
702 isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
703 &Name = "")</tt><p>
705 Create a new global variable of the specified type. If <tt>isConstant</tt> is
706 true then the global variable will be marked as unchanging for the program, and
707 if <tt>isInternal</tt> is true the resultant global variable will have internal
708 linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
711 <li><tt>bool isConstant() const</tt><p>
713 Returns true if this is a global variable is known not to be modified at
717 <li><tt>bool hasInitializer()</tt><p>
719 Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
722 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
724 Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
725 this method if there is no initializer.<p>
728 <!-- ======================================================================= -->
729 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
730 <tr><td> </td><td width="100%">
731 <font color="#EEEEFF" face="Georgia,Palatino"><b>
732 <a name="Module">The <tt>Module</tt> class</a>
733 </b></font></td></tr></table><ul>
736 href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
737 doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
739 The <tt>Module</tt> class represents the top level structure present in LLVM
740 programs. An LLVM module is effectively either a translation unit of the
741 original program or a combination of several translation units merged by the
742 linker. The <tt>Module</tt> class keeps track of a list of <a
743 href="#Function"><tt>Function</tt></a>s, a list of <a
744 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
745 href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
746 helpful member functions that try to make common operations easy.<p>
749 <!-- _______________________________________________________________________ -->
750 </ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
751 <tt>Module</tt> class</h4><ul>
753 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
754 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
755 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
756 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
758 These are forwarding methods that make it easy to access the contents of a
759 <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
762 <li><tt>Module::FunctionListType &getFunctionList()</tt><p>
764 Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
765 neccesary to use when you need to update the list or perform a complex action
766 that doesn't have a forwarding method.<p>
768 <!-- Global Variable -->
771 <li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
772 <tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
773 <tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
774 <tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
776 These are forwarding methods that make it easy to access the contents of a
777 <tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
780 <li><tt>Module::GlobalListType &getGlobalList()</tt><p>
782 Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
783 This is neccesary to use when you need to update the list or perform a complex
784 action that doesn't have a forwarding method.<p>
787 <!-- Symbol table stuff -->
790 <li><tt>bool hasSymbolTable() const</tt><p>
792 Return true if the <tt>Module</tt> has a symbol table allocated to it and if
793 there is at least one entry in it.<p>
795 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
797 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
798 <tt>Module</tt> or a null pointer if one has not been allocated (because there
799 are no named values in the function).<p>
801 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
803 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
804 <tt>Module</tt> or allocate a new <a
805 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
806 should only be used when adding elements to the <a
807 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
808 not left laying around.<p>
811 <!-- Convenience methods -->
814 <li><tt><a href="#Function">Function</a> *getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt><p>
816 Look up the specified function in the <tt>Module</tt> <a
817 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
821 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
822 &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
824 Look up the specified function in the <tt>Module</tt> <a
825 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
826 external declaration for the function and return it.<p>
829 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
831 If there is at least one entry in the <a
832 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
833 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
837 <li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
840 Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
841 <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
842 is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
846 <!-- ======================================================================= -->
847 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
848 <tr><td> </td><td width="100%">
849 <font color="#EEEEFF" face="Georgia,Palatino"><b>
850 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
851 </b></font></td></tr></table><ul>
853 Constant represents a base class for different types of constants. It is
854 subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
855 ConstantArray etc for representing the various types of Constants.<p>
858 <!-- _______________________________________________________________________ -->
859 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
861 <li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
866 \subsection{Important Subclasses of Constant}
868 <li>ConstantSInt : This subclass of Constant represents a signed integer constant.
870 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
872 <li>ConstantUInt : This class represents an unsigned integer.
874 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
876 <li>ConstantFP : This class represents a floating point constant.
878 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
880 <li>ConstantBool : This represents a boolean constant.
882 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
884 <li>ConstantArray : This represents a constant array.
886 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
888 <li>ConstantStruct : This represents a constant struct.
890 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
892 <li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
894 <li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
899 <!-- ======================================================================= -->
900 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
901 <tr><td> </td><td width="100%">
902 <font color="#EEEEFF" face="Georgia,Palatino"><b>
903 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
904 </b></font></td></tr></table><ul>
906 Type as noted earlier is also a subclass of a Value class. Any primitive
907 type (like int, short etc) in LLVM is an instance of Type Class. All
908 other types are instances of subclasses of type like FunctionType,
909 ArrayType etc. DerivedType is the interface for all such dervied types
910 including FunctionType, ArrayType, PointerType, StructType. Types can have
911 names. They can be recursive (StructType). There exists exactly one instance
912 of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
914 <!-- _______________________________________________________________________ -->
915 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
917 <li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
918 <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.
919 <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.
920 <li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
921 <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.
923 <li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
924 <li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
925 <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.
926 <li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
927 <li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
928 <li><tt>const Type * getContainedType (unsigned i) const</tt>:
929 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.
930 <li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
934 \subsection{Derived Types}
936 <li>SequentialType : This is subclassed by ArrayType and PointerType
938 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
940 <li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
942 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
944 <li>PointerType : Subclass of SequentialType for pointer types.
945 <li>StructType : subclass of DerivedTypes for struct types
946 <li>FunctionType : subclass of DerivedTypes for function types.
949 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
950 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
951 <li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
952 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
953 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
960 <!-- ======================================================================= -->
961 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
962 <tr><td> </td><td width="100%">
963 <font color="#EEEEFF" face="Georgia,Palatino"><b>
964 <a name="Argument">The <tt>Argument</tt> class</a>
965 </b></font></td></tr></table><ul>
967 This subclass of Value defines the interface for incoming formal arguments to a
968 function. A Function maitanis a list of its formal arguments. An argument has a
969 pointer to the parent Function.
974 <!-- *********************************************************************** -->
976 <!-- *********************************************************************** -->
979 <address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
980 <a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
981 <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
983 Last modified: Fri Sep 6 11:39:58 CDT 2002
985 </font></body></html>