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Initial checkin of the first part of the Programmer's Manual There is still much to be done, but it's a good start. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3589 91177308-0d34-0410-b5e6-96231b3b80d8
2002-09-06 02:50:58 +00:00
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>LLVM Programmer's Manual</title></head>
<body bgcolor=white>
<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp; <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>LLVM Programmer's Manual</b></font></td>
</tr></table>
<ol>
<li><a href="#introduction">Introduction</a>
<li><a href="#general">General Information</a>
<ul>
<li><a href="#stl">The C++ Standard Template Library</a>
<li>The isa&lt;&gt;, cast&lt;&gt; and dyn_cast&lt;&gt; templates
</ul>
<li><a href="#coreclasses">The Core LLVM Class Heirarchy</a>
<ul>
<li><a href="#Value">The <tt>Value</tt> class</a>
<ul>
<li><a href="#User">The <tt>User</tt> class</a>
<ul>
<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
<ul>
<li>
<li>
</ul>
<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
<ul>
<li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a>
<li><a href="#Function">The <tt>Function</tt> class</a>
<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a>
</ul>
<li><a href="#Module">The <tt>Module</tt> class</a>
<li><a href="#Constant">The <tt>Constant</tt> class</a>
<ul>
<li>
<li>
</ul>
</ul>
<li><a href="#Type">The <tt>Type</tt> class</a>
<li><a href="#Argument">The <tt>Argument</tt> class</a>
</ul>
<li>The <tt>SymbolTable</tt> class
<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
<ul>
<li>Creating, inserting, moving and deleting from LLVM lists
</ul>
<li>Important iterator invalidation semantics to be aware of
</ul>
<!--
III. Useful things to know about the LLVM source base:
III.1 Useful links that introduce the STL
III.2 isa<>, cast<>, dyn_cast<>
III.3 Makefiles, useful options
III.4 How to use opt & analyze to debug stuff
III.5 How to write a regression test
III.6 DEBUG() and Statistics (-debug & -stats)
III.7 The -time-passes option
III.8 ... more as needed ...
-->
<p><b>Written by <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>
and <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
</ol>
<!-- *********************************************************************** -->
<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="introduction">Introduction
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
This document is meant to hi-light some of the important classes and interfaces
available in the LLVM source-base. This manual is not indended to explain what
LLVM is, how it works, and what LLVM code looks like. It assumes that you know
the basics of LLVM and are interested in writing transformations or otherwise
analyzing or manipulating the code.<p>
This document should get you oriented so that you can find your way in the
continuously growing source code that makes up the LLVM infrastructure. Note
that this manual is not intended to serve as a replacement for reading the
source code, so if you think there should be a method in one of these classes to
do something, but it's not listed, check the source. Links to the <a
href="/doxygen/">doxygen</a> sources are provided to make this as easy as
possible.<p>
The first section of this document describes general information that is useful
to know when working in the LLVM infrastructure, and the second describes the
Core LLVM classes. In the future this manual will be extended with information
describing how to use extension libraries, such as dominator information, CFG
traversal routines, and useful utilities like the <tt><a
href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
<!-- *********************************************************************** -->
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="general">General Information
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
This section contains general information that is useful if you are working in
the LLVM source-base, but that isn't specific to any particular API.<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="stl">The C++ Standard Template Library</a>
</b></font></td></tr></table><ul>
LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
more than you are used to, or have seen before. Because of this, you might want
to do a little background reading in the techniques used and capabilities of the
library. There are many good pages that discuss the STL, and several books on
the subject that you can get, so it will not be discussed in this document.<p>
Here are some useful links:<p>
<ol>
<li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
Library reference</a> - an excellent reference for the STL and other parts of
the standard C++ library.<br>
<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
Questions</a>
<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
Contains a useful <a
href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
STL</a>.
<li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
Page</a>
</ol><p>
You are also encouraged to take a look at the <a
href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
to write maintainable code more than where to put your curly braces.<p>
<!-- *********************************************************************** -->
</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
<a name="coreclasses">The Core LLVM Class Heirarchy
</b></font></td></tr></table><ul>
<!-- *********************************************************************** -->
The Core LLVM classes are the primary means of representing the program being
inspected or transformed. The core LLVM classes are defined in header files in
the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
directory.<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="Value">The <tt>Value</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
The <tt>Value</tt> class is the most important class in LLVM Source base. It
represents a typed value that may be used (among other things) as an operand to
an instruction. There are many different types of <tt>Value</tt>s, such as <a
href="#Constant"><tt>Constant</tt></a>s, <a
href="#Argument"><tt>Argument</tt></a>s, and even <a
href="#Instruction"><tt>Instruction</tt></a>s and <a
href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
A particular <tt>Value</tt> may be used many times in the LLVM representation
for a program. For example, an incoming argument to a function (represented
with an instance of the <a href="#Argument">Argument</a> class) is "used" by
every instruction in the function that references the argument. To keep track
of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
href="#User"><tt>User</tt></a>s that is using it (the <a
href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
def-use information in the program, and is accessable through the <tt>use_</tt>*
methods, shown below.<p>
Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
method. <a name="#nameWarning">In addition, all LLVM values can be named. The
"name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
<pre>
%<b>foo</b> = add int 1, 2
</pre>
The name of this instruction is "foo". <b>NOTE</b> that the name of any value
may be missing (an empty string), so names should <b>ONLY</b> be used for
debugging (making the source code easier to read, debugging printouts), they
should not be used to keep track of values or map between them. For this
purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
instead.<p>
One important aspect of LLVM is that there is no distinction between an SSA
variable and the operation that produces it. Because of this, any reference to
the value produced by an instruction (or the value available as an incoming
argument, for example) is represented as a direct pointer to the class that
represents this value. Although this may take some getting used to, it
simplifies the representation and makes it easier to manipulate.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_Value"><hr size=0>Important Public Members of
the <tt>Value</tt> class</h4><ul>
<li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
<tt>Value::use_const_iterator</tt>
- Typedef for const_iterator over the use-list<br>
<tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
<tt>bool use_empty()</tt> - Returns true if there are no users.<br>
<tt>use_iterator use_begin()</tt>
- Get an iterator to the start of the use-list.<br>
<tt>use_iterator use_end()</tt>
- Get an iterator to the end of the use-list.<br>
<tt><a href="#User">User</a> *use_back()</tt>
- Returns the last element in the list.<p>
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>
<li><tt><a href="#Type">Type</a> *getType() const</tt><p>
This method returns the Type of the Value.
<li><tt>bool hasName() const</tt><br>
<tt>std::string getName() const</tt><br>
<tt>void setName(const std::string &amp;Name)</tt><p>
This family of methods is used to access and assign a name to a <tt>Value</tt>,
be aware of the <a href="#nameWarning">precaution above</a>.<p>
<li><tt>void replaceAllUsesWith(Value *V)</tt><p>
This method traverses the use list of a <tt>Value</tt> changing all <a
href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
instead. For example, if you detect that an instruction always produces a
constant value (for example through constant folding), you can replace all uses
of the instruction with the constant like this:<p>
<pre>
Inst-&gt;replaceAllUsesWith(ConstVal);
</pre><p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="User">The <tt>User</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
Superclass: <a href="#Value"><tt>Value</tt></a><p>
The <tt>User</tt> class is the common base class of all LLVM nodes that may
refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
referring to. The <tt>User</tt> class itself is a subclass of
<tt>Value</tt>.<p>
The operands of a <tt>User</tt> point directly to the LLVM <a
href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
Single Assignment (SSA) form, there can only be one definition referred to,
allowing this direct connection. This connection provides the use-def
information in LLVM.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_User"><hr size=0>Important Public Members of
the <tt>User</tt> class</h4><ul>
The <tt>User</tt> class exposes the operand list in two ways: through an index
access interface and through an iterator based interface.<p>
<li><tt>Value *getOperand(unsigned i)</tt><br>
<tt>unsigned getNumOperands()</tt><p>
These two methods expose the operands of the <tt>User</tt> in a convenient form
for direct access.<p>
<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
<tt>User::op_const_iterator</tt>
<tt>use_iterator op_begin()</tt>
- Get an iterator to the start of the operand list.<br>
<tt>use_iterator op_end()</tt>
- Get an iterator to the end of the operand list.<p>
Together, these methods make up the iterator based interface to the operands of
a <tt>User</tt>.<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="Instruction">The <tt>Instruction</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a
href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
Superclasses: <a href="#User"><tt>User</tt></a>, <a
href="#Value"><tt>Value</tt></a><p>
The <tt>Instruction</tt> class is the common base class for all LLVM
instructions. It provides only a few methods, but is a very commonly used
class. The primary data tracked by the <tt>Instruction</tt> class itself is the
opcode (instruction type) and the parent <a
href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
into. To represent a specific type of instruction, one of many subclasses of
<tt>Instruction</tt> are used.<p>
Because the <tt>Instruction</tt> class subclasses the <a
href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
way as for other <a href="#User"><tt>User</tt></a>s (with the
<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
<tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
the <tt>Instruction</tt> class</h4><ul>
<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
<tt>Instruction</tt> is embedded into.<p>
<li><tt>bool hasSideEffects()</tt><p>
Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
<li><tt>unsigned getOpcode()</tt><p>
Returns the opcode for the <tt>Instruction</tt>.<p>
<!--
\subsection{Subclasses of Instruction :}
\begin{itemize}
<li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
\begin{itemize}
<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.
\end{itemize}
<li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
\begin{itemize}
<li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
<li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
<li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
\end{itemize}
<li>PHINode : This represents the PHI instructions in the SSA form.
\begin{itemize}
<li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
<li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
<li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
<li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
<li><tt> void addIncoming(Value *D, BasicBlock *BB)</tt>:
Add an incoming value to the end of the PHI list
<li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
\end{itemize}
<li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
<li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
\begin{itemize}
<li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
\end{itemize}
<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
\begin{itemize}
<li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
\end{itemize}
<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
\begin{itemize}
<li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
<li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
<li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
\end{itemize}
\end{itemize}
-->
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a
href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
Superclass: <a href="#Value"><tt>Value</tt></a><p>
This class represents a single entry multiple exit section of the code, commonly
known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
the body of the block. Matching the language definition, the last element of
this list of instructions is always a terminator instruction (a subclass of the
<a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
In addition to tracking the list of instructions that make up the block, the
<tt>BasicBlock</tt> class also keeps track of the <a
href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
Note that <tt>BasicBlock</tt>s themselves are <a
href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
<tt>label</tt>.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
the <tt>BasicBlock</tt> class</h4><ul>
<li><tt>BasicBlock(const std::string &amp;Name = "", <a
href="#Function">Function</a> *Parent = 0)</tt><p>
The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
insertion into a function. The constructor simply takes a name for the new
block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
into. If the <tt>Parent</tt> parameter is specified, the new
<tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
These methods and typedefs are forwarding functions that have the same semantics
as the standard library methods of the same names. These methods expose the
underlying instruction list of a basic block in a way that is easy to
manipulate. To get the full complement of container operations (including
operations to update the list), you must use the <tt>getInstList()</tt>
method.<p>
<li><tt>BasicBlock::InstListType &amp;getInstList()</tt><p>
This method is used to get access to the underlying container that actually
holds the Instructions. This method must be used when there isn't a forwarding
function in the <tt>BasicBlock</tt> class for the operation that you would like
to perform. Because there are no forwarding functions for "updating"
operations, you need to use this if you want to update the contents of a
<tt>BasicBlock</tt>.<p>
<li><tt><A href="#Function">Function</a> *getParent()</tt><p>
Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
embedded into, or a null pointer if it is homeless.<p>
<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
Returns a pointer to the terminator instruction that appears at the end of the
<tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
instruction in the block is not a terminator, then a null pointer is
returned.<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a
href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
Superclasses: <a href="#User"><tt>User</tt></a>, <a
href="#Value"><tt>Value</tt></a><p>
Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
Because they are visible at global scope, they are also subject to linking with
other globals defined in different translation units. To control the linking
process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
<tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
<tt>static</tt> in C), it is not visible to code outside the current translation
unit, and does not participate in linking. If it has external linkage, it is
visible to external code, and does participate in linking. In addition to
linkage information, <tt>GlobalValue</tt>s keep track of which <a
href="#Module"><tt>Module</tt></a> they are currently part of.<p>
Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
always a pointer to its contents. This is explained in the LLVM Language
Reference Manual.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
the <tt>GlobalValue</tt> class</h4><ul>
<li><tt>bool hasInternalLinkage() const</tt><br>
<tt>bool hasExternalLinkage() const</tt><br>
<tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
These methods manipulate the linkage characteristics of the
<tt>GlobalValue</tt>.<p>
<li><tt><a href="#Module">Module</a> *getParent()</tt><p>
This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
currently embedded into.<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="Function">The <tt>Function</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a
href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
The <tt>Function</tt> class represents a single procedure in LLVM. It is
actually one of the more complex classes in the LLVM heirarchy because it must
keep track of a large amount of data. The <tt>Function</tt> class keeps track
of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
href="#Argument"><tt>Argument</tt></a>s, and a <a
href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
used part of <tt>Function</tt> objects. The list imposes an implicit ordering
of the blocks in the function, which indicate how the code will be layed out by
the backend. Additionally, the first <a
href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
<tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
block. There are no implicit exit nodes, and in fact there may be multiple exit
nodes from a single <tt>Function</tt>. If the <a
href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
the <tt>Function</tt> is actually a function declaration: the actual body of the
function hasn't been linked in yet.<p>
In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
<tt>Function</tt> class also keeps track of the list of formal <a
href="#Argument"><tt>Argument</tt></a>s that the function receives. This
container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
feature that is only used when you have to look up a value by name. Aside from
that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
make sure that there are not conflicts between the names of <a
href="#Instruction"><tt>Instruction</tt></a>s, <a
href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_Function"><hr size=0>Important Public Members of
the <tt>Function</tt> class</h4><ul>
<li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &amp;N = "")</tt><p>
Constructor used when you need to create new <tt>Function</tt>s to add the the
program. The constructor must specify the type of the function to create and
whether or not it should start out with internal or external linkage.<p>
<li><tt>bool isExternal()</tt><p>
Return whether or not the <tt>Function</tt> has a body defined. If the function
is "external", it does not have a body, and thus must be resolved by linking
with a function defined in a different translation unit.<p>
<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
These are forwarding methods that make it easy to access the contents of a
<tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
list.<p>
<li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt><p>
Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
neccesary to use when you need to update the list or perform a complex action
that doesn't have a forwarding method.<p>
<li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
These are forwarding methods that make it easy to access the contents of a
<tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
<li><tt>Function::ArgumentListType &amp;getArgumentList()</tt><p>
Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
neccesary to use when you need to update the list or perform a complex action
that doesn't have a forwarding method.<p>
<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
function. Because the entry block for the function is always the first block,
this returns the first block of the <tt>Function</tt>.<p>
<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
and returns the return type of the function, or the <a
href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
<li><tt>bool hasSymbolTable() const</tt><p>
Return true if the <tt>Function</tt> has a symbol table allocated to it and if
there is at least one entry in it.<p>
<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
<tt>Function</tt> or a null pointer if one has not been allocated (because there
are no named values in the function).<p>
<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
<tt>Function</tt> or allocate a new <a
href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
should only be used when adding elements to the <a
href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
not left laying around.<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
</b></font></td></tr></table><ul>
<tt>#include "<a
href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
A GlobalVariable is a subclass of GlobalValue and defines the interface to
global variables in the SSA program. It can have a name and an
initializer. (initial constant Value)
Can be constant.
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of
the <tt>GlobalVariable</tt> class</h4><ul>
<li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
&amp;Name = "")</tt><p>
<li><tt>bool isConstant() const</tt><p>
Returns true if this is a global variable is known not to be modified at
runtime.<p>
<li><tt>bool hasInitializer()</tt><p>
Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
Returns the intializer<p>
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
</b></font></td></tr></table><ul>
Constant represents a base class for different types of constants. It is
subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
ConstantArray etc for representing the various types of Constants.<p>
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
\subsection{Important Subclasses of Constant}
\begin{itemize}
<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
\begin{itemize}
<li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
\end{itemize}
<li>ConstantUInt : This class represents an unsigned integer.
\begin{itemize}
<li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
\end{itemize}
<li>ConstantFP : This class represents a floating point constant.
\begin{itemize}
<li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
\end{itemize}
<li>ConstantBool : This represents a boolean constant.
\begin{itemize}
<li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
\end{itemize}
<li>ConstantArray : This represents a constant array.
\begin{itemize}
<li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
\end{itemize}
<li>ConstantStruct : This represents a constant struct.
\begin{itemize}
<li><tt>const std::vector<Use> &amp;getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
\end{itemize}
<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
\begin{itemize}
<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
\end{itemize}
\end{itemize}
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="Type">The <tt>Type</tt> class and Derived Types</a>
</b></font></td></tr></table><ul>
Type as noted earlier is also a subclass of a Value class. Any primitive
type (like int, short etc) in LLVM is an instance of Type Class. All
other types are instances of subclasses of type like FunctionType,
ArrayType etc. DerivedType is the interface for all such dervied types
including FunctionType, ArrayType, PointerType, StructType. Types can have
names. They can be recursive (StructType). There exists exactly one instance
of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
<!-- _______________________________________________________________________ -->
</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
<li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
<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.
<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.
<li><tt> bool isInteger () const</tt>: Equilivent to isSigned() || isUnsigned(), but with only a single virtual function invocation.
<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.
<li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
<li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
<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.
<li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
<li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
<li><tt>const Type * getContainedType (unsigned i) const</tt>:
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.
<li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
\subsection{Derived Types}
\begin{itemize}
<li>SequentialType : This is subclassed by ArrayType and PointerType
\begin{itemize}
<li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
\end{itemize}
<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
\begin{itemize}
<li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
\end{itemize}
<li>PointerType : Subclass of SequentialType for pointer types.
<li>StructType : subclass of DerivedTypes for struct types
<li>FunctionType : subclass of DerivedTypes for function types.
\begin{itemize}
<li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
<li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
<li><tt> const ParamTypes &amp;getParamTypes () const</tt>: Returns a vector of parameter types.
<li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
<li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
\end{itemize}
\end{itemize}
<!-- ======================================================================= -->
</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
<tr><td>&nbsp;</td><td width="100%">&nbsp;
<font color="#EEEEFF" face="Georgia,Palatino"><b>
<a name="Argument">The <tt>Argument</tt> class</a>
</b></font></td></tr></table><ul>
This subclass of Value defines the interface for incoming formal arguments to a
function. A Function maitanis a list of its formal arguments. An argument has a
pointer to the parent Function.
<!-- *********************************************************************** -->
</ul>
<!-- *********************************************************************** -->
<hr><font size-1>
<address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
<!-- hhmts start -->
Last modified: Thu Sep 5 21:49:34 CDT 2002
<!-- hhmts end -->
</font></body></html>
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