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2 <html><head><title>LLVM Programmer's Manual</title></head>
7 <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
8 <tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM Programmer's Manual</b></font></td>
12 <li><a href="#introduction">Introduction</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</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>
150 <!-- *********************************************************************** -->
151 </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
152 <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
153 <a name="coreclasses">The Core LLVM Class Heirarchy
154 </b></font></td></tr></table><ul>
155 <!-- *********************************************************************** -->
157 The Core LLVM classes are the primary means of representing the program being
158 inspected or transformed. The core LLVM classes are defined in header files in
159 the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
163 <!-- ======================================================================= -->
164 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
165 <tr><td> </td><td width="100%">
166 <font color="#EEEEFF" face="Georgia,Palatino"><b>
167 <a name="Value">The <tt>Value</tt> class</a>
168 </b></font></td></tr></table><ul>
170 <tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
171 doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
174 The <tt>Value</tt> class is the most important class in LLVM Source base. It
175 represents a typed value that may be used (among other things) as an operand to
176 an instruction. There are many different types of <tt>Value</tt>s, such as <a
177 href="#Constant"><tt>Constant</tt></a>s, <a
178 href="#Argument"><tt>Argument</tt></a>s, and even <a
179 href="#Instruction"><tt>Instruction</tt></a>s and <a
180 href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
182 A particular <tt>Value</tt> may be used many times in the LLVM representation
183 for a program. For example, an incoming argument to a function (represented
184 with an instance of the <a href="#Argument">Argument</a> class) is "used" by
185 every instruction in the function that references the argument. To keep track
186 of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
187 href="#User"><tt>User</tt></a>s that is using it (the <a
188 href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
189 graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
190 def-use information in the program, and is accessable through the <tt>use_</tt>*
191 methods, shown below.<p>
193 Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
194 this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
195 method. <a name="#nameWarning">In addition, all LLVM values can be named. The
196 "name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
199 %<b>foo</b> = add int 1, 2
202 The name of this instruction is "foo". <b>NOTE</b> that the name of any value
203 may be missing (an empty string), so names should <b>ONLY</b> be used for
204 debugging (making the source code easier to read, debugging printouts), they
205 should not be used to keep track of values or map between them. For this
206 purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
209 One important aspect of LLVM is that there is no distinction between an SSA
210 variable and the operation that produces it. Because of this, any reference to
211 the value produced by an instruction (or the value available as an incoming
212 argument, for example) is represented as a direct pointer to the class that
213 represents this value. Although this may take some getting used to, it
214 simplifies the representation and makes it easier to manipulate.<p>
217 <!-- _______________________________________________________________________ -->
218 </ul><h4><a name="m_Value"><hr size=0>Important Public Members of
219 the <tt>Value</tt> class</h4><ul>
221 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
222 <tt>Value::use_const_iterator</tt>
223 - Typedef for const_iterator over the use-list<br>
224 <tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
225 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
226 <tt>use_iterator use_begin()</tt>
227 - Get an iterator to the start of the use-list.<br>
228 <tt>use_iterator use_end()</tt>
229 - Get an iterator to the end of the use-list.<br>
230 <tt><a href="#User">User</a> *use_back()</tt>
231 - Returns the last element in the list.<p>
233 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>
235 <li><tt><a href="#Type">Type</a> *getType() const</tt><p>
236 This method returns the Type of the Value.
238 <li><tt>bool hasName() const</tt><br>
239 <tt>std::string getName() const</tt><br>
240 <tt>void setName(const std::string &Name)</tt><p>
242 This family of methods is used to access and assign a name to a <tt>Value</tt>,
243 be aware of the <a href="#nameWarning">precaution above</a>.<p>
246 <li><tt>void replaceAllUsesWith(Value *V)</tt><p>
248 This method traverses the use list of a <tt>Value</tt> changing all <a
249 href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
250 instead. For example, if you detect that an instruction always produces a
251 constant value (for example through constant folding), you can replace all uses
252 of the instruction with the constant like this:<p>
255 Inst->replaceAllUsesWith(ConstVal);
260 <!-- ======================================================================= -->
261 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
262 <tr><td> </td><td width="100%">
263 <font color="#EEEEFF" face="Georgia,Palatino"><b>
264 <a name="User">The <tt>User</tt> class</a>
265 </b></font></td></tr></table><ul>
267 <tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
268 doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
269 Superclass: <a href="#Value"><tt>Value</tt></a><p>
272 The <tt>User</tt> class is the common base class of all LLVM nodes that may
273 refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
274 that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
275 referring to. The <tt>User</tt> class itself is a subclass of
278 The operands of a <tt>User</tt> point directly to the LLVM <a
279 href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
280 Single Assignment (SSA) form, there can only be one definition referred to,
281 allowing this direct connection. This connection provides the use-def
282 information in LLVM.<p>
284 <!-- _______________________________________________________________________ -->
285 </ul><h4><a name="m_User"><hr size=0>Important Public Members of
286 the <tt>User</tt> class</h4><ul>
288 The <tt>User</tt> class exposes the operand list in two ways: through an index
289 access interface and through an iterator based interface.<p>
291 <li><tt>Value *getOperand(unsigned i)</tt><br>
292 <tt>unsigned getNumOperands()</tt><p>
294 These two methods expose the operands of the <tt>User</tt> in a convenient form
295 for direct access.<p>
297 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
298 <tt>User::op_const_iterator</tt>
299 <tt>use_iterator op_begin()</tt>
300 - Get an iterator to the start of the operand list.<br>
301 <tt>use_iterator op_end()</tt>
302 - Get an iterator to the end of the operand list.<p>
304 Together, these methods make up the iterator based interface to the operands of
309 <!-- ======================================================================= -->
310 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
311 <tr><td> </td><td width="100%">
312 <font color="#EEEEFF" face="Georgia,Palatino"><b>
313 <a name="Instruction">The <tt>Instruction</tt> class</a>
314 </b></font></td></tr></table><ul>
317 href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
318 doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
319 Superclasses: <a href="#User"><tt>User</tt></a>, <a
320 href="#Value"><tt>Value</tt></a><p>
322 The <tt>Instruction</tt> class is the common base class for all LLVM
323 instructions. It provides only a few methods, but is a very commonly used
324 class. The primary data tracked by the <tt>Instruction</tt> class itself is the
325 opcode (instruction type) and the parent <a
326 href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
327 into. To represent a specific type of instruction, one of many subclasses of
328 <tt>Instruction</tt> are used.<p>
330 Because the <tt>Instruction</tt> class subclasses the <a
331 href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
332 way as for other <a href="#User"><tt>User</tt></a>s (with the
333 <tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
334 <tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
337 <!-- _______________________________________________________________________ -->
338 </ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
339 the <tt>Instruction</tt> class</h4><ul>
341 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
343 Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
344 <tt>Instruction</tt> is embedded into.<p>
346 <li><tt>bool hasSideEffects()</tt><p>
348 Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
349 <tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
351 <li><tt>unsigned getOpcode()</tt><p>
353 Returns the opcode for the <tt>Instruction</tt>.<p>
357 \subsection{Subclasses of Instruction :}
359 <li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
361 <li><tt>bool swapOperands()</tt>: Exchange the two operands to this instruction. If the instruction cannot be reversed (i.e. if it's a Div), it returns true.
363 <li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
365 <li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
366 <li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
367 <li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
370 <li>PHINode : This represents the PHI instructions in the SSA form.
372 <li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
373 <li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
374 <li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
375 <li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
376 <li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
377 Add an incoming value to the end of the PHI list
378 <li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
379 Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
381 <li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
382 <li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
384 <li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
386 <li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
388 <li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
390 <li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
392 <li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
393 <li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
394 <li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
402 <!-- ======================================================================= -->
403 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
404 <tr><td> </td><td width="100%">
405 <font color="#EEEEFF" face="Georgia,Palatino"><b>
406 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
407 </b></font></td></tr></table><ul>
410 href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
411 doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
412 Superclass: <a href="#Value"><tt>Value</tt></a><p>
415 This class represents a single entry multiple exit section of the code, commonly
416 known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
417 maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
418 the body of the block. Matching the language definition, the last element of
419 this list of instructions is always a terminator instruction (a subclass of the
420 <a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
422 In addition to tracking the list of instructions that make up the block, the
423 <tt>BasicBlock</tt> class also keeps track of the <a
424 href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
426 Note that <tt>BasicBlock</tt>s themselves are <a
427 href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
428 like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
432 <!-- _______________________________________________________________________ -->
433 </ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
434 the <tt>BasicBlock</tt> class</h4><ul>
436 <li><tt>BasicBlock(const std::string &Name = "", <a
437 href="#Function">Function</a> *Parent = 0)</tt><p>
439 The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
440 insertion into a function. The constructor simply takes a name for the new
441 block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
442 into. If the <tt>Parent</tt> parameter is specified, the new
443 <tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
444 href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
445 manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
447 <li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
448 <tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
449 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
450 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
452 These methods and typedefs are forwarding functions that have the same semantics
453 as the standard library methods of the same names. These methods expose the
454 underlying instruction list of a basic block in a way that is easy to
455 manipulate. To get the full complement of container operations (including
456 operations to update the list), you must use the <tt>getInstList()</tt>
459 <li><tt>BasicBlock::InstListType &getInstList()</tt><p>
461 This method is used to get access to the underlying container that actually
462 holds the Instructions. This method must be used when there isn't a forwarding
463 function in the <tt>BasicBlock</tt> class for the operation that you would like
464 to perform. Because there are no forwarding functions for "updating"
465 operations, you need to use this if you want to update the contents of a
466 <tt>BasicBlock</tt>.<p>
468 <li><tt><A href="#Function">Function</a> *getParent()</tt><p>
470 Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
471 embedded into, or a null pointer if it is homeless.<p>
473 <li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
475 Returns a pointer to the terminator instruction that appears at the end of the
476 <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
477 instruction in the block is not a terminator, then a null pointer is
481 <!-- ======================================================================= -->
482 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
483 <tr><td> </td><td width="100%">
484 <font color="#EEEEFF" face="Georgia,Palatino"><b>
485 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
486 </b></font></td></tr></table><ul>
489 href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
490 doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
491 Superclasses: <a href="#User"><tt>User</tt></a>, <a
492 href="#Value"><tt>Value</tt></a><p>
494 Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
495 href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
496 visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
497 Because they are visible at global scope, they are also subject to linking with
498 other globals defined in different translation units. To control the linking
499 process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
500 <tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
502 If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
503 <tt>static</tt> in C), it is not visible to code outside the current translation
504 unit, and does not participate in linking. If it has external linkage, it is
505 visible to external code, and does participate in linking. In addition to
506 linkage information, <tt>GlobalValue</tt>s keep track of which <a
507 href="#Module"><tt>Module</tt></a> they are currently part of.<p>
509 Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
510 their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
511 always a pointer to its contents. This is explained in the LLVM Language
515 <!-- _______________________________________________________________________ -->
516 </ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
517 the <tt>GlobalValue</tt> class</h4><ul>
519 <li><tt>bool hasInternalLinkage() const</tt><br>
520 <tt>bool hasExternalLinkage() const</tt><br>
521 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
523 These methods manipulate the linkage characteristics of the
524 <tt>GlobalValue</tt>.<p>
526 <li><tt><a href="#Module">Module</a> *getParent()</tt><p>
528 This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
529 currently embedded into.<p>
533 <!-- ======================================================================= -->
534 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
535 <tr><td> </td><td width="100%">
536 <font color="#EEEEFF" face="Georgia,Palatino"><b>
537 <a name="Function">The <tt>Function</tt> class</a>
538 </b></font></td></tr></table><ul>
541 href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
542 doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
543 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
544 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
546 The <tt>Function</tt> class represents a single procedure in LLVM. It is
547 actually one of the more complex classes in the LLVM heirarchy because it must
548 keep track of a large amount of data. The <tt>Function</tt> class keeps track
549 of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
550 href="#Argument"><tt>Argument</tt></a>s, and a <a
551 href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
553 The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
554 used part of <tt>Function</tt> objects. The list imposes an implicit ordering
555 of the blocks in the function, which indicate how the code will be layed out by
556 the backend. Additionally, the first <a
557 href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
558 <tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
559 block. There are no implicit exit nodes, and in fact there may be multiple exit
560 nodes from a single <tt>Function</tt>. If the <a
561 href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
562 the <tt>Function</tt> is actually a function declaration: the actual body of the
563 function hasn't been linked in yet.<p>
565 In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
566 <tt>Function</tt> class also keeps track of the list of formal <a
567 href="#Argument"><tt>Argument</tt></a>s that the function receives. This
568 container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
569 nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
570 the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
572 The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
573 feature that is only used when you have to look up a value by name. Aside from
574 that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
575 make sure that there are not conflicts between the names of <a
576 href="#Instruction"><tt>Instruction</tt></a>s, <a
577 href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
578 href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
581 <!-- _______________________________________________________________________ -->
582 </ul><h4><a name="m_Function"><hr size=0>Important Public Members of
583 the <tt>Function</tt> class</h4><ul>
585 <li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
587 Constructor used when you need to create new <tt>Function</tt>s to add the the
588 program. The constructor must specify the type of the function to create and
589 whether or not it should start out with internal or external linkage.<p>
591 <li><tt>bool isExternal()</tt><p>
593 Return whether or not the <tt>Function</tt> has a body defined. If the function
594 is "external", it does not have a body, and thus must be resolved by linking
595 with a function defined in a different translation unit.<p>
598 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
599 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
600 <tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
601 <tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
603 These are forwarding methods that make it easy to access the contents of a
604 <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
607 <li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
609 Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
610 neccesary to use when you need to update the list or perform a complex action
611 that doesn't have a forwarding method.<p>
614 <li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
615 <tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
616 <tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
617 <tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
619 These are forwarding methods that make it easy to access the contents of a
620 <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
622 <li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
624 Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
625 neccesary to use when you need to update the list or perform a complex action
626 that doesn't have a forwarding method.<p>
630 <li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
632 Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
633 function. Because the entry block for the function is always the first block,
634 this returns the first block of the <tt>Function</tt>.<p>
636 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
637 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
639 This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
640 and returns the return type of the function, or the <a
641 href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
644 <li><tt>bool hasSymbolTable() const</tt><p>
646 Return true if the <tt>Function</tt> has a symbol table allocated to it and if
647 there is at least one entry in it.<p>
649 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
651 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
652 <tt>Function</tt> or a null pointer if one has not been allocated (because there
653 are no named values in the function).<p>
655 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
657 Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
658 <tt>Function</tt> or allocate a new <a
659 href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
660 should only be used when adding elements to the <a
661 href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
662 not left laying around.<p>
666 <!-- ======================================================================= -->
667 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
668 <tr><td> </td><td width="100%">
669 <font color="#EEEEFF" face="Georgia,Palatino"><b>
670 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
671 </b></font></td></tr></table><ul>
674 href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
675 doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
676 Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
677 href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
680 A GlobalVariable is a subclass of GlobalValue and defines the interface to
681 global variables in the SSA program. It can have a name and an
682 initializer. (initial constant Value)
687 <!-- _______________________________________________________________________ -->
688 </ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of
689 the <tt>GlobalVariable</tt> class</h4><ul>
691 <li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
692 isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
693 &Name = "")</tt><p>
695 <li><tt>bool isConstant() const</tt><p>
697 Returns true if this is a global variable is known not to be modified at
700 <li><tt>bool hasInitializer()</tt><p>
702 Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
704 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
706 Returns the intializer<p>
708 <!-- ======================================================================= -->
709 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
710 <tr><td> </td><td width="100%">
711 <font color="#EEEEFF" face="Georgia,Palatino"><b>
712 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
713 </b></font></td></tr></table><ul>
715 Constant represents a base class for different types of constants. It is
716 subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
717 ConstantArray etc for representing the various types of Constants.<p>
720 <!-- _______________________________________________________________________ -->
721 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
723 <li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
728 \subsection{Important Subclasses of Constant}
730 <li>ConstantSInt : This subclass of Constant represents a signed integer constant.
732 <li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
734 <li>ConstantUInt : This class represents an unsigned integer.
736 <li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
738 <li>ConstantFP : This class represents a floating point constant.
740 <li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
742 <li>ConstantBool : This represents a boolean constant.
744 <li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
746 <li>ConstantArray : This represents a constant array.
748 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
750 <li>ConstantStruct : This represents a constant struct.
752 <li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
754 <li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
756 <li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
761 <!-- ======================================================================= -->
762 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
763 <tr><td> </td><td width="100%">
764 <font color="#EEEEFF" face="Georgia,Palatino"><b>
765 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
766 </b></font></td></tr></table><ul>
768 Type as noted earlier is also a subclass of a Value class. Any primitive
769 type (like int, short etc) in LLVM is an instance of Type Class. All
770 other types are instances of subclasses of type like FunctionType,
771 ArrayType etc. DerivedType is the interface for all such dervied types
772 including FunctionType, ArrayType, PointerType, StructType. Types can have
773 names. They can be recursive (StructType). There exists exactly one instance
774 of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
776 <!-- _______________________________________________________________________ -->
777 </ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
779 <li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
780 <li><tt> bool isSigned () const</tt>: Returns whether an integral numeric type is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is not true for Float and Double.
781 <li><tt>bool isUnsigned () const</tt>: Returns whether a numeric type is unsigned. This is not quite the complement of isSigned... nonnumeric types return false as they do with isSigned. This returns true for UByteTy, UShortTy, UIntTy, and ULongTy.
782 <li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
783 <li><tt>bool isIntegral () const</tt>: Returns true if this is an integral type, which is either Bool type or one of the Integer types.
785 <li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
786 <li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
787 <li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if this type can be converted to 'Ty' without any reinterpretation of bits. For example, uint to int.
788 <li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
789 <li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
790 <li><tt>const Type * getContainedType (unsigned i) const</tt>:
791 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.
792 <li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
796 \subsection{Derived Types}
798 <li>SequentialType : This is subclassed by ArrayType and PointerType
800 <li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
802 <li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
804 <li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
806 <li>PointerType : Subclass of SequentialType for pointer types.
807 <li>StructType : subclass of DerivedTypes for struct types
808 <li>FunctionType : subclass of DerivedTypes for function types.
811 <li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
812 <li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
813 <li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
814 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
815 <li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
822 <!-- ======================================================================= -->
823 </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
824 <tr><td> </td><td width="100%">
825 <font color="#EEEEFF" face="Georgia,Palatino"><b>
826 <a name="Argument">The <tt>Argument</tt> class</a>
827 </b></font></td></tr></table><ul>
829 This subclass of Value defines the interface for incoming formal arguments to a
830 function. A Function maitanis a list of its formal arguments. An argument has a
831 pointer to the parent Function.
836 <!-- *********************************************************************** -->
838 <!-- *********************************************************************** -->
841 <address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
842 <a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
843 <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
845 Last modified: Thu Sep 5 21:49:34 CDT 2002
847 </font></body></html>