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				2	<html><head><title>LLVM Programmer's Manual</title></head>
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				4	<body bgcolor=white>
				5
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	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>
				8	</tr></table>
				9
				10	<ol>
				11	<li><a href="#introduction">Introduction</a>
				12	<li><a href="#general">General Information</a>
				13	<ul>
				14	<li><a href="#stl">The C++ Standard Template Library</a>
Chris Lattner	1d43fd4	2002-09-09 05:53:21 +0000	[diff] [blame]	15	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt> and
				16	<tt>dyn_cast<></tt> templates</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	17	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	18	<li><a href="#common">Helpful Hints for Common Operations</a>
				19	<ul>
				20	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				21	<ul>
				22	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				23	in a <tt>Function</tt></a>
				24	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				25	in a <tt>BasicBlock</tt></a>
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	26	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				27	in a <tt>Function</tt></a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	28	<li><a href="#iterate_convert">Turning an iterator into a class
				29	pointer</a>
Chris Lattner	f1ebdc3	2002-09-06 22:09:21 +0000	[diff] [blame]	30	<li><a href="#iterate_complex">Finding call sites: a more complex
				31	example</a>
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	32	<li><a href="#iterate_chains">Iterating over def-use & use-def
				33	chains</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	34	</ul>
				35	<li><a href="#simplechanges">Making simple changes</a>
				36	<ul>
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	37	<li><a href="#schanges_creating">Creating and inserting new
				38	<tt>Instruction</tt>s</a>
				39	<li><a href="#schanges_deleting">Deleting
				40	<tt>Instruction</tt>s</a>
				41	<li><a href="#schanges_replacing">Replacing an
				42	<tt>Instruction</tt> with another <tt>Value</tt></a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	43	</ul>
				44	<!--
				45	<li>Working with the Control Flow Graph
				46	<ul>
				47	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				48	<li>
				49	<li>
				50	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	51	<li>Useful LLVM APIs
				52	<ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	53	<li>The general graph API
				54	<li>The <tt>InstVisitor</tt> template
				55	<li>The DEBUG() macro
				56	<li>The <tt>Statistic</tt> template
				57	-->
				58	</ul>
				59	<!--
				60	<li>Useful related topics
				61	<ul>
				62	<li>The <tt>-time-passes</tt> option
				63	<li>How to use the LLVM Makefile system
				64	<li>How to write a regression test
				65	<li>
				66	</ul>
				67	-->
				68	</ul>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	69	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	70	<ul>
				71	<li><a href="#Value">The <tt>Value</tt> class</a>
				72	<ul>
				73	<li><a href="#User">The <tt>User</tt> class</a>
				74	<ul>
				75	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
				76	<ul>
				77	<li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	78	</ul>
				79	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				80	<ul>
				81	<li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a>
				82	<li><a href="#Function">The <tt>Function</tt> class</a>
				83	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				84	</ul>
				85	<li><a href="#Module">The <tt>Module</tt> class</a>
				86	<li><a href="#Constant">The <tt>Constant</tt> class</a>
				87	<ul>
				88	<li>
				89	<li>
				90	</ul>
				91	</ul>
				92	<li><a href="#Type">The <tt>Type</tt> class</a>
				93	<li><a href="#Argument">The <tt>Argument</tt> class</a>
				94	</ul>
				95	<li>The <tt>SymbolTable</tt> class
				96	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				97	<ul>
				98	<li>Creating, inserting, moving and deleting from LLVM lists
				99	</ul>
				100	<li>Important iterator invalidation semantics to be aware of
				101	</ul>
				102
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	103	<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
				104	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>, and
Chris Lattner	f1ebdc3	2002-09-06 22:09:21 +0000	[diff] [blame]	105	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a></b><p>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	106	</ol>
				107
				108
				109	<!-- *********************************************************************** -->
				110	<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
				111	<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				112	<a name="introduction">Introduction
				113	</b></font></td></tr></table><ul>
				114	<!-- *********************************************************************** -->
				115
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	116	This document is meant to highlight some of the important classes and interfaces
				117	available in the LLVM source-base. This manual is not intended to explain what
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	118	LLVM is, how it works, and what LLVM code looks like. It assumes that you know
				119	the basics of LLVM and are interested in writing transformations or otherwise
				120	analyzing or manipulating the code.<p>
				121
				122	This document should get you oriented so that you can find your way in the
				123	continuously growing source code that makes up the LLVM infrastructure. Note
				124	that this manual is not intended to serve as a replacement for reading the
				125	source code, so if you think there should be a method in one of these classes to
				126	do something, but it's not listed, check the source. Links to the <a
				127	href="/doxygen/">doxygen</a> sources are provided to make this as easy as
				128	possible.<p>
				129
				130	The first section of this document describes general information that is useful
				131	to know when working in the LLVM infrastructure, and the second describes the
				132	Core LLVM classes. In the future this manual will be extended with information
				133	describing how to use extension libraries, such as dominator information, CFG
				134	traversal routines, and useful utilities like the <tt><a
				135	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.<p>
				136
				137
				138	<!-- *********************************************************************** -->
				139	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
				140	<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				141	<a name="general">General Information
				142	</b></font></td></tr></table><ul>
				143	<!-- *********************************************************************** -->
				144
				145	This section contains general information that is useful if you are working in
				146	the LLVM source-base, but that isn't specific to any particular API.<p>
				147
				148
				149	<!-- ======================================================================= -->
				150	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				151	<tr><td> </td><td width="100%">
				152	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				153	<a name="stl">The C++ Standard Template Library</a>
				154	</b></font></td></tr></table><ul>
				155
				156	LLVM makes heavy use of the C++ Standard Template Library (STL), perhaps much
				157	more than you are used to, or have seen before. Because of this, you might want
				158	to do a little background reading in the techniques used and capabilities of the
				159	library. There are many good pages that discuss the STL, and several books on
				160	the subject that you can get, so it will not be discussed in this document.<p>
				161
				162	Here are some useful links:<p>
				163	<ol>
				164	<li><a href="http://www.dinkumware.com/htm_cpl/index.html">Dinkumware C++
				165	Library reference</a> - an excellent reference for the STL and other parts of
				166	the standard C++ library.<br>
				167
				168	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				169	Questions</a>
				170
				171	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				172	Contains a useful <a
				173	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				174	STL</a>.
				175
				176	<li><a href="http://www.research.att.com/~bs/C++.html">Bjarne Stroustrup's C++
				177	Page</a>
				178
				179	</ol><p>
				180
				181	You are also encouraged to take a look at the <a
				182	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				183	to write maintainable code more than where to put your curly braces.<p>
				184
				185
Chris Lattner	1d43fd4	2002-09-09 05:53:21 +0000	[diff] [blame]	186	<!-- ======================================================================= -->
				187	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				188	<tr><td> </td><td width="100%">
				189	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				190	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				191	</b></font></td></tr></table><ul>
				192
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	193	The LLVM source-base makes extensive use of a custom form of RTTI. These
				194	templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				195	operator, but they don't have some drawbacks (primarily stemming from the fact
				196	that <tt>dynamic_cast<></tt> only works on classes that have a v-table).
				197	Because they are used so often, you must know what they do and how they work.
				198	All of these templates are defined in the <a
				199	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a> file (note
				200	that you very rarely have to include this file directly).<p>
Chris Lattner	1d43fd4	2002-09-09 05:53:21 +0000	[diff] [blame]	201
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	202	<dl>
				203
				204	<dt><tt>isa<></tt>:
				205
				206	<dd>The <tt>isa<></tt> operator works exactly like the Java
				207	"<tt>instanceof</tt>" operator. It returns true or false depending on whether a
				208	reference or pointer points to an instance of the specified class. This can be
				209	very useful for constraint checking of various sorts (example below).<p>
				210
				211
				212	<dt><tt>cast<></tt>:
				213
				214	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				215	converts a pointer or reference from a base class to a derived cast, causing an
				216	assertion failure if it is not really an instance of the right type. This
				217	should be used in cases where you have some information that makes you believe
				218	that something is of the right type. An example of the <tt>isa<></tt> and
				219	<tt>cast<></tt> template is:<p>
				220
				221	<pre>
				222	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				223	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				224	return true;
				225
				226	<i>// Otherwise, it must be an instruction...</i>
				227	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				228	</pre><p>
				229
				230	Note that you should <b>not</b> use an <tt>isa<></tt> test followed by a
				231	<tt>cast<></tt>, for that use the <tt>dyn_cast<></tt> operator.<p>
				232
				233
				234	<dt><tt>dyn_cast<></tt>:
				235
				236	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				237	checks to see if the operand is of the specified type, and if so, returns a
				238	pointer to it (this operator does not work with references). If the operand is
				239	not of the correct type, a null pointer is returned. Thus, this works very much
				240	like the <tt>dynamic_cast</tt> operator in C++, and should be used in the same
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	241	circumstances. Typically, the <tt>dyn_cast<></tt> operator is used in an
				242	<tt>if</tt> statement or some other flow control statement like this:<p>
				243
				244	<pre>
				245	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				246	...
				247	}
				248	</pre><p>
				249
				250	This form of the <tt>if</tt> statement effectively combines together a call to
				251	<tt>isa<></tt> and a call to <tt>cast<></tt> into one statement,
				252	which is very convenient.<p>
				253
				254	Another common example is:<p>
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	255
				256	<pre>
				257	<i>// Loop over all of the phi nodes in a basic block</i>
				258	BasicBlock::iterator BBI = BB->begin();
				259	for (; <a href="#PhiNode">PHINode</a> PN = dyn_cast<<a href="#PHINode">PHINode</a>>(&BBI); ++BBI)
				260	cerr << *PN;
				261	</pre><p>
				262
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	263	Note that the <tt>dyn_cast<></tt> operator, like C++'s
				264	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused. In
				265	particular you should not use big chained <tt>if/then/else</tt> blocks to check
				266	for lots of different variants of classes. If you find yourself wanting to do
				267	this, it is much cleaner and more efficient to use the InstVisitor class to
				268	dispatch over the instruction type directly.<p>
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	269
				270
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	271	<dt><tt>cast_or_null<></tt>:
				272
				273	<dd>The <tt>cast_or_null<></tt> operator works just like the
				274	<tt>cast<></tt> operator, except that it allows for a null pointer as an
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	275	argument (which it then propagates). This can sometimes be useful, allowing you
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	276	to combine several null checks into one.<p>
				277
				278
				279	<dt><tt>dyn_cast_or_null<></tt>:
				280
				281	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				282	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer as
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	283	an argument (which it then propagates). This can sometimes be useful, allowing
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	284	you to combine several null checks into one.<p>
				285
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	286	</dl>
Chris Lattner	1d43fd4	2002-09-09 05:53:21 +0000	[diff] [blame]	287
Chris Lattner	6b121f1	2002-09-10 15:20:46 +0000	[diff] [blame]	288	These five templates can be used with any classes, whether they have a v-table
				289	or not. To add support for these templates, you simply need to add
				290	<tt>classof</tt> static methods to the class you are interested casting to.
				291	Describing this is currently outside the scope of this document, but there are
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	292	lots of examples in the LLVM source base.<p>
Chris Lattner	1d43fd4	2002-09-09 05:53:21 +0000	[diff] [blame]	293
				294
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	295
Chris Lattner	b99344f	2002-09-06 16:40:10 +0000	[diff] [blame]	296	<!-- *********************************************************************** -->
				297	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
				298	<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
				299	<a name="common">Helpful Hints for Common Operations
				300	</b></font></td></tr></table><ul>
				301	<!-- *********************************************************************** -->
				302
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	303	This section describes how to perform some very simple transformations of LLVM
				304	code. This is meant to give examples of common idioms used, showing the
				305	practical side of LLVM transformations.<p>
				306
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	307	Because this is a "how-to" section, you should also read about the main classes
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	308	that you will be working with. The <a href="#coreclasses">Core LLVM Class
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	309	Hierarchy Reference</a> contains details and descriptions of the main classes
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	310	that you should know about.<p>
				311
				312	<!-- NOTE: this section should be heavy on example code -->
				313
				314
				315	<!-- ======================================================================= -->
				316	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				317	<tr><td> </td><td width="100%">
				318	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				319	<a name="inspection">Basic Inspection and Traversal Routines</a>
				320	</b></font></td></tr></table><ul>
				321
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	322	The LLVM compiler infrastructure have many different data structures that may be
				323	traversed. Following the example of the C++ standard template library, the
				324	techniques used to traverse these various data structures are all basically the
				325	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				326	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				327	function returns an iterator pointing to one past the last valid element of the
				328	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				329	between the two operations.<p>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	330
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	331	Because the pattern for iteration is common across many different aspects of the
				332	program representation, the standard template library algorithms may be used on
				333	them, and it is easier to remember how to iterate. First we show a few common
				334	examples of the data structures that need to be traversed. Other data
				335	structures are traversed in very similar ways.<p>
				336
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	337
				338	<!-- _______________________________________________________________________ -->
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	339	</ul><h4><a name="iterate_function"><hr size=0>Iterating over the <a
				340	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				341	href="#Function"><tt>Function</tt></a> </h4><ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	342
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	343	It's quite common to have a <tt>Function</tt> instance that you'd like
				344	to transform in some way; in particular, you'd like to manipulate its
				345	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over
				346	all of the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>.
				347	The following is an example that prints the name of a
				348	<tt>BasicBlock</tt> and the number of <tt>Instruction</tt>s it
				349	contains:
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	350
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	351	<pre>
				352	// func is a pointer to a Function instance
				353	for(Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {
				354
				355	// print out the name of the basic block if it has one, and then the
				356	// number of instructions that it contains
				357
Joel Stanley	72ef35e	2002-09-06 23:05:12 +0000	[diff] [blame]	358	cerr <&lt "Basic block (name=" <&lt i->getName() << ") has "
				359	<&lt i->size() <&lt " instructions.\n";
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	360	}
				361	</pre>
				362
				363	Note that i can be used as if it were a pointer for the purposes of
				364	invoking member functions of the <tt>Instruction</tt> class. This is
				365	because the indirection operator is overloaded for the iterator
				366	classes. In the above code, the expression <tt>i->size()</tt> is
				367	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	368
				369	<!-- _______________________________________________________________________ -->
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	370	</ul><h4><a name="iterate_basicblock"><hr size=0>Iterating over the <a
				371	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				372	href="#BasicBlock"><tt>BasicBlock</tt></a> </h4><ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	373
Joel Stanley	aaeb1c1	2002-09-06 23:42:40 +0000	[diff] [blame]	374	Just like when dealing with <tt>BasicBlock</tt>s in
				375	<tt>Function</tt>s, it's easy to iterate over the individual
				376	instructions that make up <tt>BasicBlock</tt>s. Here's a code snippet
				377	that prints out each instruction in a <tt>BasicBlock</tt>:
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	378
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	379	<pre>
				380	// blk is a pointer to a BasicBlock instance
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	381	for(BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
Chris Lattner	2b76306	2002-09-06 22:51:10 +0000	[diff] [blame]	382	// the next statement works since operator<<(ostream&,...)
				383	// is overloaded for Instruction&
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	384	cerr << *i << "\n";
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	385	</pre>
				386
				387	However, this isn't really the best way to print out the contents of a
				388	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for
				389	virtually anything you'll care about, you could have just invoked the
Chris Lattner	2b76306	2002-09-06 22:51:10 +0000	[diff] [blame]	390	print routine on the basic block itself: <tt>cerr << *blk <<
				391	"\n";</tt>.<p>
				392
				393	Note that currently operator<< is implemented for <tt>Value*</tt>, so it
				394	will print out the contents of the pointer, instead of
				395	the pointer value you might expect. This is a deprecated interface that will
				396	be removed in the future, so it's best not to depend on it. To print out the
				397	pointer value for now, you must cast to <tt>void*</tt>.<p>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	398
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	399
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	400	<!-- _______________________________________________________________________ -->
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	401	</ul><h4><a name="iterate_institer"><hr size=0>Iterating over the <a
				402	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				403	href="#Function"><tt>Function</tt></a></h4><ul>
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	404
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	405	If you're finding that you commonly iterate over a <tt>Function</tt>'s
				406	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s
				407	<tt>Instruction</tt>s, <tt>InstIterator</tt> should be used instead.
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	408	You'll need to include <a href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>, and then
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	409	instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
				410	small example that shows how to dump all instructions in a function to
				411	stderr (<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
				412	<tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&amp</tt>!):
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	413
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	414	<pre>
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	415	#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	416	...
				417	// Suppose F is a ptr to a function
				418	for(inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
				419	cerr <&lt **i <&lt "\n";
				420	</pre>
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	421
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	422	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				423	worklist with its initial contents. For example, if you wanted to
				424	initialize a worklist to contain all instructions in a
				425	<tt>Function</tt> F, all you would need to do is something like:
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	426
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	427	<pre>
				428	std::set<Instruction*&gt worklist;
				429	worklist.insert(inst_begin(F), inst_end(F));
				430	</pre>
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	431
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	432	The STL set <tt>worklist</tt> would now contain all instructions in
				433	the <tt>Function</tt> pointed to by F.
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	434
				435	<!-- _______________________________________________________________________ -->
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	436	</ul><h4><a name="iterate_convert"><hr size=0>Turning an iterator into a class
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	437	pointer (and vice-versa) </h4><ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	438
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	439	Sometimes, it'll be useful to grab a reference (or pointer) to a class
				440	instance when all you've got at hand is an iterator. Well, extracting
				441	a reference or a pointer from an iterator is very straightforward.
				442	Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and
				443	<tt>j</tt> is a <tt>BasicBlock::const_iterator</tt>:
				444
				445	<pre>
Chris Lattner	83b5ee0	2002-09-06 22:12:58 +0000	[diff] [blame]	446	Instruction& inst = *i; // grab reference to instruction reference
				447	Instruction* pinst = &*i; // grab pointer to instruction reference
				448	const Instruction& inst = *j;
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	449	</pre>
				450	However, the iterators you'll be working with in the LLVM framework
				451	are special: they will automatically convert to a ptr-to-instance type
				452	whenever they need to. Instead of dereferencing the iterator and then
				453	taking the address of the result, you can simply assign the iterator
				454	to the proper pointer type and you get the dereference and address-of
				455	operation as a result of the assignment (behind the scenes, this is a
				456	result of overloading casting mechanisms). Thus the last line of the
				457	last example,
				458
Chris Lattner	83b5ee0	2002-09-06 22:12:58 +0000	[diff] [blame]	459	<pre>Instruction* pinst = &*i;</pre>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	460
				461	is semantically equivalent to
				462
				463	<pre>Instruction* pinst = i;</pre>
				464
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	465	<b>Caveat emptor</b>: The above syntax works <i>only</i> when you're <i>not</i>
				466	working with <tt>dyn_cast</tt>. The template definition of <tt><a
				467	href="#isa">dyn_cast</a></tt> isn't implemented to handle this yet, so you'll
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	468	still need the following in order for things to work properly:
				469
				470	<pre>
				471	BasicBlock::iterator bbi = ...;
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	472	<a href="#BranchInst">BranchInst</a>* b = <a href="#isa">dyn_cast</a><<a href="#BranchInst">BranchInst</a>>(&*bbi);
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	473	</pre>
				474
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	475	It's also possible to turn a class pointer into the corresponding
				476	iterator. Usually, this conversion is quite inexpensive. The
				477	following code snippet illustrates use of the conversion constructors
				478	provided by LLVM iterators. By using these, you can explicitly grab
				479	the iterator of something without actually obtaining it via iteration
				480	over some structure:
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	481
				482	<pre>
				483	void printNextInstruction(Instruction* inst) {
				484	BasicBlock::iterator it(inst);
				485	++it; // after this line, it refers to the instruction after *inst.
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	486	if(it != inst->getParent()->end()) cerr << *it << "\n";
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	487	}
				488	</pre>
Joel Stanley	aaeb1c1	2002-09-06 23:42:40 +0000	[diff] [blame]	489	Of course, this example is strictly pedagogical, because it'd be much
				490	better to explicitly grab the next instruction directly from inst.
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	491
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	492
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	493	<!--_______________________________________________________________________-->
				494	</ul><h4><a name="iterate_complex"><hr size=0>Finding call sites: a slightly
				495	more complex example </h4><ul>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	496
				497	Say that you're writing a FunctionPass and would like to count all the
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	498	locations in the entire module (that is, across every
Joel Stanley	d8aabb2	2002-09-09 16:29:58 +0000	[diff] [blame]	499	<tt>Function</tt>) where a certain function (i.e. some
				500	<tt>Function</tt>*) already in scope. As you'll learn later, you may
				501	want to use an <tt>InstVisitor</tt> to accomplish this in a much more
				502	straightforward manner, but this example will allow us to explore how
				503	you'd do it if you didn't have <tt>InstVisitor</tt> around. In
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	504	pseudocode, this is what we want to do:
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	505
				506	<pre>
				507	initialize callCounter to zero
				508	for each Function f in the Module
				509	for each BasicBlock b in f
				510	for each Instruction i in b
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	511	if(i is a CallInst and calls the given function)
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	512	increment callCounter
				513	</pre>
				514
				515	And the actual code is (remember, since we're writing a
Joel Stanley	d8aabb2	2002-09-09 16:29:58 +0000	[diff] [blame]	516	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	517	has to override the <tt>runOnFunction</tt> method...):
				518
				519	<pre>
Joel Stanley	d8aabb2	2002-09-09 16:29:58 +0000	[diff] [blame]	520	Function* targetFunc = ...;
				521
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	522	class OurFunctionPass : public FunctionPass {
				523	public:
Joel Stanley	d8aabb2	2002-09-09 16:29:58 +0000	[diff] [blame]	524	OurFunctionPass(): callCounter(0) { }
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	525
Chris Lattner	caa5d13	2002-09-09 19:58:18 +0000	[diff] [blame]	526	virtual runOnFunction(Function& F) {
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	527	for(Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
				528	for(BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {
Chris Lattner	979d9b7	2002-09-10 00:39:05 +0000	[diff] [blame]	529	if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a href="#CallInst">CallInst</a>>(&*inst)) {
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	530	// we know we've encountered a call instruction, so we
				531	// need to determine if it's a call to the
				532	// function pointed to by m_func or not.
				533
Joel Stanley	d8aabb2	2002-09-09 16:29:58 +0000	[diff] [blame]	534	if(callInst->getCalledFunction() == targetFunc)
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	535	++callCounter;
				536	}
				537	}
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	538	}
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	539
				540	private:
Joel Stanley	d8aabb2	2002-09-09 16:29:58 +0000	[diff] [blame]	541	unsigned callCounter;
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	542	};
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	543	</pre>
				544
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	545	<!--_______________________________________________________________________-->
				546	</ul><h4><a name="iterate_chains"><hr size=0>Iterating over def-use &
				547	use-def chains</h4><ul>
				548
Joel Stanley	01040b2	2002-09-11 20:50:04 +0000	[diff] [blame]	549	Frequently, we might have an instance of the <a
				550	href="/doxygen/classValue.html">Value Class</a> and we want to
				551	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of
				552	all <tt>User</tt>s of a particular <tt>Value</tt> is called a
				553	<i>def-use</i> chain. For example, let's say we have a
				554	<tt>Function*</tt> named <tt>F</tt> to a particular function
				555	<tt>foo</tt>. Finding all of the instructions that <i>use</i>
				556	<tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain of
				557	<tt>F</tt>:
				558
				559	<pre>
				560	Function* F = ...;
				561
				562	for(Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {
				563	if(Instruction* i = dyn_cast<Instruction>(*i)) {
				564	cerr << "F is used in instruction:\n\t";
				565	cerr << *i << "\n";
				566	}
				567	}
				568	</pre>
				569
				570	Alternately, it's common to have an instance of the <a
				571	href="/doxygen/classUser.html">User Class</a> and need to know what
				572	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used
				573	by a <tt>User</tt> is known as a <i>use-def</i> chain. Instances of
				574	class <tt>Instruction</tt> are common <tt>User</tt>s, so we might want
				575	to iterate over all of the values that a particular instruction uses
				576	(that is, the operands of the particular <tt>Instruction</tt>):
				577
				578	<pre>
				579	Instruction* pi = ...;
				580
				581	for(User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	582	Value* v = *i;
Joel Stanley	01040b2	2002-09-11 20:50:04 +0000	[diff] [blame]	583	...
				584	}
				585	</pre>
				586
				587
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	588	<!--
				589	def-use chains ("finding all users of"): Value::use_begin/use_end
				590	use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
				591	-->
				592
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	593	<!-- ======================================================================= -->
				594	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				595	<tr><td> </td><td width="100%">
				596	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				597	<a name="simplechanges">Making simple changes</a>
				598	</b></font></td></tr></table><ul>
				599
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	600	There are some primitive transformation operations present in the LLVM
				601	infrastructure that are worth knowing about. When performing
				602	transformations, it's fairly common to manipulate the contents of
				603	basic blocks. This section describes some of the common methods for
				604	doing so and gives example code.
				605
				606	<!--_______________________________________________________________________-->
				607	</ul><h4><a name="schanges_creating"><hr size=0>Creating and inserting
				608	new <tt>Instruction</tt>s</h4><ul>
				609
				610	<i>Instantiating Instructions</i>
				611
				612	<p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
				613	constructor for the kind of instruction to instantiate and provide the
				614	necessary parameters. For example, an <tt>AllocaInst</tt> only
				615	<i>requires</i> a (const-ptr-to) <tt>Type</tt>. Thus:
				616
				617	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				618
				619	will create an <tt>AllocaInst</tt> instance that represents the
				620	allocation of one integer in the current stack frame, at runtime.
				621	Each <tt>Instruction</tt> subclass is likely to have varying default
				622	parameters which change the semantics of the instruction, so refer to
Chris Lattner	4e1f96b	2002-09-12 19:06:51 +0000	[diff] [blame^]	623	the <a href="/doxygen/classInstruction.html">doxygen documentation for
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	624	the subclass of Instruction</a> that you're interested in
				625	instantiating.</p>
				626
				627	<p><i>Naming values</i></p>
				628
				629	<p>
				630	It is very useful to name the values of instructions when you're able
				631	to, as this facilitates the debugging of your transformations. If you
				632	end up looking at generated LLVM machine code, you definitely want to
				633	have logical names associated with the results of instructions! By
				634	supplying a value for the <tt>Name</tt> (default) parameter of the
				635	<tt>Instruction</tt> constructor, you associate a logical name with
				636	the result of the instruction's execution at runtime. For example,
				637	say that I'm writing a transformation that dynamically allocates space
				638	for an integer on the stack, and that integer is going to be used as
				639	some kind of index by some other code. To accomplish this, I place an
				640	<tt>AllocaInst</tt> at the first point in the first
				641	<tt>BasicBlock</tt> of some <tt>Function</tt>, and I'm intending to
				642	use it within the same <tt>Function</tt>. I might do:
				643
				644	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				645
				646	where <tt>indexLoc</tt> is now the logical name of the instruction's
				647	execution value, which is a pointer to an integer on the runtime
				648	stack.
				649	</p>
				650
				651	<p><i>Inserting instructions</i></p>
				652
				653	<p>
				654	There are essentially two ways to insert an <tt>Instruction</tt> into
				655	an existing sequence of instructions that form a <tt>BasicBlock</tt>:
				656	<ul>
				657	<li>Insertion into an explicit instruction list
				658
				659	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within
				660	that <tt>BasicBlock</tt>, and a newly-created instruction
				661	we wish to insert before <tt>*pi</tt>, we do the following:
				662
				663	<pre>
				664	BasicBlock* pb = ...;
				665	Instruction* pi = ...;
				666	Instruction* newInst = new Instruction(...);
				667	pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb
				668	</pre>
				669	</p>
				670
				671	<li>Insertion into an implicit instruction list
				672	<p>
				673	<tt>Instruction</tt> instances that are already in
				674	<tt>BasicBlock</tt>s are implicitly associated with an existing
				675	instruction list: the instruction list of the enclosing basic block.
				676	Thus, we could have accomplished the same thing as the above code
				677	without being given a <tt>BasicBlock</tt> by doing:
				678	<pre>
				679	Instruction* pi = ...;
				680	Instruction* newInst = new Instruction(...);
				681	pi->getParent()->getInstList().insert(pi, newInst);
				682	</pre>
				683	In fact, this sequence of steps occurs so frequently that the
				684	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes
				685	provide constructors which take (as a default parameter) a pointer to
				686	an <tt>Instruction</tt> which the newly-created <tt>Instruction</tt>
				687	should precede. That is, <tt>Instruction</tt> constructors are
				688	capable of inserting the newly-created instance into the
				689	<tt>BasicBlock</tt> of a provided instruction, immediately before that
				690	instruction. Using an <tt>Instruction</tt> constructor with a
				691	<tt>insertBefore</tt> (default) parameter, the above code becomes:
				692	<pre>
				693	Instruction* pi = ...;
				694	Instruction* newInst = new Instruction(..., pi);
				695	</pre>
				696	which is much cleaner, especially if you're creating a lot of
				697	instructions and adding them to <tt>BasicBlock</tt>s.
				698	</p>
				699	</p>
				700
				701
				702	<!--_______________________________________________________________________-->
				703	</ul><h4><a name="schanges_deleting"><hr size=0>Deleting
Chris Lattner	4e1f96b	2002-09-12 19:06:51 +0000	[diff] [blame^]	704	<tt>Instruction</tt>s</h4><ul>
				705
				706	Deleting an instruction from an existing sequence of instructions that form a <a
				707	href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First, you
				708	must have a pointer to the instruction that you wish to delete. Second, you
				709	need to obtain the pointer to that instruction's basic block. You use the
				710	pointer to the basic block to get its list of instructions and then use the
				711	erase function to remove your instruction.<p>
				712
				713	For example:<p>
				714
				715	<pre>
				716	<a href="#Instruction">Instruction</a> *I = .. ;
				717	<a href="#BasicBlock">BasicBlock</a> *BB = I->getParent();
				718	BB->getInstList().erase(I);
				719	</pre><p>
				720
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	721
				722	<!--_______________________________________________________________________-->
				723	</ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
				724	<tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
				725
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	726	<!-- Value::replaceAllUsesWith
				727	User::replaceUsesOfWith
				728	Point out: include/llvm/Transforms/Utils/
				729	especially BasicBlockUtils.h with:
				730	ReplaceInstWithValue, ReplaceInstWithInst
				731
				732	-->
Chris Lattner	b99344f	2002-09-06 16:40:10 +0000	[diff] [blame]	733
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	734	<!-- *********************************************************************** -->
				735	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
				736	<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	737	<a name="coreclasses">The Core LLVM Class Hierarchy Reference
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	738	</b></font></td></tr></table><ul>
				739	<!-- *********************************************************************** -->
				740
				741	The Core LLVM classes are the primary means of representing the program being
				742	inspected or transformed. The core LLVM classes are defined in header files in
				743	the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
				744	directory.<p>
				745
				746
				747	<!-- ======================================================================= -->
				748	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				749	<tr><td> </td><td width="100%">
				750	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				751	<a name="Value">The <tt>Value</tt> class</a>
				752	</b></font></td></tr></table><ul>
				753
				754	<tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
				755	doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
				756
				757
				758	The <tt>Value</tt> class is the most important class in LLVM Source base. It
				759	represents a typed value that may be used (among other things) as an operand to
				760	an instruction. There are many different types of <tt>Value</tt>s, such as <a
				761	href="#Constant"><tt>Constant</tt></a>s, <a
				762	href="#Argument"><tt>Argument</tt></a>s, and even <a
				763	href="#Instruction"><tt>Instruction</tt></a>s and <a
				764	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
				765
				766	A particular <tt>Value</tt> may be used many times in the LLVM representation
				767	for a program. For example, an incoming argument to a function (represented
				768	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				769	every instruction in the function that references the argument. To keep track
				770	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				771	href="#User"><tt>User</tt></a>s that is using it (the <a
				772	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				773	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	774	def-use information in the program, and is accessible through the <tt>use_</tt>*
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	775	methods, shown below.<p>
				776
				777	Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
				778	this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				779	method. <a name="#nameWarning">In addition, all LLVM values can be named. The
				780	"name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
				781
				782	<pre>
				783	%<b>foo</b> = add int 1, 2
				784	</pre>
				785
				786	The name of this instruction is "foo". <b>NOTE</b> that the name of any value
				787	may be missing (an empty string), so names should <b>ONLY</b> be used for
				788	debugging (making the source code easier to read, debugging printouts), they
				789	should not be used to keep track of values or map between them. For this
				790	purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
				791	instead.<p>
				792
				793	One important aspect of LLVM is that there is no distinction between an SSA
				794	variable and the operation that produces it. Because of this, any reference to
				795	the value produced by an instruction (or the value available as an incoming
				796	argument, for example) is represented as a direct pointer to the class that
				797	represents this value. Although this may take some getting used to, it
				798	simplifies the representation and makes it easier to manipulate.<p>
				799
				800
				801	<!-- _______________________________________________________________________ -->
				802	</ul><h4><a name="m_Value"><hr size=0>Important Public Members of
				803	the <tt>Value</tt> class</h4><ul>
				804
				805	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
				806	<tt>Value::use_const_iterator</tt>
				807	- Typedef for const_iterator over the use-list<br>
				808	<tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
				809	<tt>bool use_empty()</tt> - Returns true if there are no users.<br>
				810	<tt>use_iterator use_begin()</tt>
				811	- Get an iterator to the start of the use-list.<br>
				812	<tt>use_iterator use_end()</tt>
				813	- Get an iterator to the end of the use-list.<br>
				814	<tt><a href="#User">User</a> *use_back()</tt>
				815	- Returns the last element in the list.<p>
				816
				817	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>
				818
				819	<li><tt><a href="#Type">Type</a> *getType() const</tt><p>
				820	This method returns the Type of the Value.
				821
				822	<li><tt>bool hasName() const</tt><br>
				823	<tt>std::string getName() const</tt><br>
				824	<tt>void setName(const std::string &Name)</tt><p>
				825
				826	This family of methods is used to access and assign a name to a <tt>Value</tt>,
				827	be aware of the <a href="#nameWarning">precaution above</a>.<p>
				828
				829
				830	<li><tt>void replaceAllUsesWith(Value *V)</tt><p>
				831
				832	This method traverses the use list of a <tt>Value</tt> changing all <a
				833	href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
				834	instead. For example, if you detect that an instruction always produces a
				835	constant value (for example through constant folding), you can replace all uses
				836	of the instruction with the constant like this:<p>
				837
				838	<pre>
				839	Inst->replaceAllUsesWith(ConstVal);
				840	</pre><p>
				841
				842
				843
				844	<!-- ======================================================================= -->
				845	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				846	<tr><td> </td><td width="100%">
				847	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				848	<a name="User">The <tt>User</tt> class</a>
				849	</b></font></td></tr></table><ul>
				850
				851	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
				852	doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
				853	Superclass: <a href="#Value"><tt>Value</tt></a><p>
				854
				855
				856	The <tt>User</tt> class is the common base class of all LLVM nodes that may
				857	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				858	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				859	referring to. The <tt>User</tt> class itself is a subclass of
				860	<tt>Value</tt>.<p>
				861
				862	The operands of a <tt>User</tt> point directly to the LLVM <a
				863	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				864	Single Assignment (SSA) form, there can only be one definition referred to,
				865	allowing this direct connection. This connection provides the use-def
				866	information in LLVM.<p>
				867
				868	<!-- _______________________________________________________________________ -->
				869	</ul><h4><a name="m_User"><hr size=0>Important Public Members of
				870	the <tt>User</tt> class</h4><ul>
				871
				872	The <tt>User</tt> class exposes the operand list in two ways: through an index
				873	access interface and through an iterator based interface.<p>
				874
				875	<li><tt>Value *getOperand(unsigned i)</tt><br>
				876	<tt>unsigned getNumOperands()</tt><p>
				877
				878	These two methods expose the operands of the <tt>User</tt> in a convenient form
				879	for direct access.<p>
				880
				881	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
				882	<tt>User::op_const_iterator</tt>
				883	<tt>use_iterator op_begin()</tt>
				884	- Get an iterator to the start of the operand list.<br>
				885	<tt>use_iterator op_end()</tt>
				886	- Get an iterator to the end of the operand list.<p>
				887
				888	Together, these methods make up the iterator based interface to the operands of
				889	a <tt>User</tt>.<p>
				890
				891
				892
				893	<!-- ======================================================================= -->
				894	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				895	<tr><td> </td><td width="100%">
				896	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				897	<a name="Instruction">The <tt>Instruction</tt> class</a>
				898	</b></font></td></tr></table><ul>
				899
				900	<tt>#include "<a
				901	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
				902	doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
				903	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				904	href="#Value"><tt>Value</tt></a><p>
				905
				906	The <tt>Instruction</tt> class is the common base class for all LLVM
				907	instructions. It provides only a few methods, but is a very commonly used
				908	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				909	opcode (instruction type) and the parent <a
				910	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				911	into. To represent a specific type of instruction, one of many subclasses of
				912	<tt>Instruction</tt> are used.<p>
				913
				914	Because the <tt>Instruction</tt> class subclasses the <a
				915	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				916	way as for other <a href="#User"><tt>User</tt></a>s (with the
				917	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				918	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
				919
Chris Lattner	1763525	2002-09-12 17:18:46 +0000	[diff] [blame]	920	An important file for the <tt>Instruction</tt> class is the
				921	<tt>llvm/Instruction.def</tt> file. This file contains some meta-data about the
				922	various different types of instructions in LLVM. It describes the enum values
				923	that are used as opcodes (for example <tt>Instruction::Add</tt> and
				924	<tt>Instruction::SetLE</tt>), as well as the concrete sub-classes of
				925	<tt>Instruction</tt> that implement the instruction (for example <tt><a
				926	href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				927	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				928	this file confused doxygen, so these enum values don't show up correctly in the
				929	<a href="/doxygen/classInstruction.html">doxygen output</a>.<p>
				930
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	931
				932	<!-- _______________________________________________________________________ -->
				933	</ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
				934	the <tt>Instruction</tt> class</h4><ul>
				935
				936	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
				937
				938	Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
				939	<tt>Instruction</tt> is embedded into.<p>
				940
				941	<li><tt>bool hasSideEffects()</tt><p>
				942
				943	Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
				944	<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
				945
				946	<li><tt>unsigned getOpcode()</tt><p>
				947
				948	Returns the opcode for the <tt>Instruction</tt>.<p>
				949
Chris Lattner	1763525	2002-09-12 17:18:46 +0000	[diff] [blame]	950	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt><p>
				951
				952	Returns another instance of the specified instruction, identical in all ways to
				953	the original except that the instruction has no parent (ie it's not embedded
				954	into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>), and it has no name.<p>
				955
				956
				957
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	958	<!--
				959
				960	\subsection{Subclasses of Instruction :}
				961	\begin{itemize}
				962	<li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
				963	\begin{itemize}
				964	<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.
				965	\end{itemize}
				966	<li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
				967	\begin{itemize}
				968	<li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
				969	<li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
				970	<li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
				971	\end{itemize}
				972
				973	<li>PHINode : This represents the PHI instructions in the SSA form.
				974	\begin{itemize}
				975	<li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
				976	<li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
				977	<li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
				978	<li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
				979	<li><tt> void addIncoming(Value D, BasicBlock BB)</tt>:
				980	Add an incoming value to the end of the PHI list
				981	<li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
				982	Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
				983	\end{itemize}
				984	<li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
				985	<li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
				986	\begin{itemize}
				987	<li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
				988	\end{itemize}
				989	<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
				990	\begin{itemize}
				991	<li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
				992	\end{itemize}
				993	<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
				994	\begin{itemize}
				995	<li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
				996	<li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
				997	<li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
				998	\end{itemize}
				999
				1000	\end{itemize}
				1001
				1002	-->
				1003
				1004
				1005	<!-- ======================================================================= -->
				1006	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1007	<tr><td> </td><td width="100%">
				1008	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1009	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1010	</b></font></td></tr></table><ul>
				1011
				1012	<tt>#include "<a
				1013	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
				1014	doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
				1015	Superclass: <a href="#Value"><tt>Value</tt></a><p>
				1016
				1017
				1018	This class represents a single entry multiple exit section of the code, commonly
				1019	known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
				1020	maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
				1021	the body of the block. Matching the language definition, the last element of
				1022	this list of instructions is always a terminator instruction (a subclass of the
				1023	<a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
				1024
				1025	In addition to tracking the list of instructions that make up the block, the
				1026	<tt>BasicBlock</tt> class also keeps track of the <a
				1027	href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
				1028
				1029	Note that <tt>BasicBlock</tt>s themselves are <a
				1030	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1031	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1032	<tt>label</tt>.<p>
				1033
				1034
				1035	<!-- _______________________________________________________________________ -->
				1036	</ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
				1037	the <tt>BasicBlock</tt> class</h4><ul>
				1038
				1039	<li><tt>BasicBlock(const std::string &Name = "", <a
				1040	href="#Function">Function</a> *Parent = 0)</tt><p>
				1041
				1042	The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1043	insertion into a function. The constructor simply takes a name for the new
				1044	block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
				1045	into. If the <tt>Parent</tt> parameter is specified, the new
				1046	<tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
				1047	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1048	manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
				1049
				1050	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1051	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1052	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1053	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
				1054
				1055	These methods and typedefs are forwarding functions that have the same semantics
				1056	as the standard library methods of the same names. These methods expose the
				1057	underlying instruction list of a basic block in a way that is easy to
				1058	manipulate. To get the full complement of container operations (including
				1059	operations to update the list), you must use the <tt>getInstList()</tt>
				1060	method.<p>
				1061
				1062	<li><tt>BasicBlock::InstListType &getInstList()</tt><p>
				1063
				1064	This method is used to get access to the underlying container that actually
				1065	holds the Instructions. This method must be used when there isn't a forwarding
				1066	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1067	to perform. Because there are no forwarding functions for "updating"
				1068	operations, you need to use this if you want to update the contents of a
				1069	<tt>BasicBlock</tt>.<p>
				1070
				1071	<li><tt><A href="#Function">Function</a> *getParent()</tt><p>
				1072
				1073	Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1074	embedded into, or a null pointer if it is homeless.<p>
				1075
				1076	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
				1077
				1078	Returns a pointer to the terminator instruction that appears at the end of the
				1079	<tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1080	instruction in the block is not a terminator, then a null pointer is
				1081	returned.<p>
				1082
				1083
				1084	<!-- ======================================================================= -->
				1085	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1086	<tr><td> </td><td width="100%">
				1087	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1088	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1089	</b></font></td></tr></table><ul>
				1090
				1091	<tt>#include "<a
				1092	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
				1093	doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
				1094	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1095	href="#Value"><tt>Value</tt></a><p>
				1096
				1097	Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1098	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1099	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1100	Because they are visible at global scope, they are also subject to linking with
				1101	other globals defined in different translation units. To control the linking
				1102	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1103	<tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
				1104
				1105	If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1106	<tt>static</tt> in C), it is not visible to code outside the current translation
				1107	unit, and does not participate in linking. If it has external linkage, it is
				1108	visible to external code, and does participate in linking. In addition to
				1109	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1110	href="#Module"><tt>Module</tt></a> they are currently part of.<p>
				1111
				1112	Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
				1113	their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
				1114	always a pointer to its contents. This is explained in the LLVM Language
				1115	Reference Manual.<p>
				1116
				1117
				1118	<!-- _______________________________________________________________________ -->
				1119	</ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
				1120	the <tt>GlobalValue</tt> class</h4><ul>
				1121
				1122	<li><tt>bool hasInternalLinkage() const</tt><br>
				1123	<tt>bool hasExternalLinkage() const</tt><br>
				1124	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
				1125
				1126	These methods manipulate the linkage characteristics of the
				1127	<tt>GlobalValue</tt>.<p>
				1128
				1129	<li><tt><a href="#Module">Module</a> *getParent()</tt><p>
				1130
				1131	This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
				1132	currently embedded into.<p>
				1133
				1134
				1135
				1136	<!-- ======================================================================= -->
				1137	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1138	<tr><td> </td><td width="100%">
				1139	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1140	<a name="Function">The <tt>Function</tt> class</a>
				1141	</b></font></td></tr></table><ul>
				1142
				1143	<tt>#include "<a
				1144	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
				1145	doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
				1146	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1147	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
				1148
				1149	The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1150	actually one of the more complex classes in the LLVM heirarchy because it must
				1151	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1152	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1153	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1154	href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
				1155
				1156	The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
				1157	used part of <tt>Function</tt> objects. The list imposes an implicit ordering
				1158	of the blocks in the function, which indicate how the code will be layed out by
				1159	the backend. Additionally, the first <a
				1160	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1161	<tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
				1162	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1163	nodes from a single <tt>Function</tt>. If the <a
				1164	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1165	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1166	function hasn't been linked in yet.<p>
				1167
				1168	In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1169	<tt>Function</tt> class also keeps track of the list of formal <a
				1170	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1171	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1172	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1173	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
				1174
				1175	The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
				1176	feature that is only used when you have to look up a value by name. Aside from
				1177	that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
				1178	make sure that there are not conflicts between the names of <a
				1179	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1180	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1181	href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
				1182
				1183
				1184	<!-- _______________________________________________________________________ -->
				1185	</ul><h4><a name="m_Function"><hr size=0>Important Public Members of
				1186	the <tt>Function</tt> class</h4><ul>
				1187
				1188	<li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
				1189
				1190	Constructor used when you need to create new <tt>Function</tt>s to add the the
				1191	program. The constructor must specify the type of the function to create and
				1192	whether or not it should start out with internal or external linkage.<p>
				1193
				1194	<li><tt>bool isExternal()</tt><p>
				1195
				1196	Return whether or not the <tt>Function</tt> has a body defined. If the function
				1197	is "external", it does not have a body, and thus must be resolved by linking
				1198	with a function defined in a different translation unit.<p>
				1199
				1200
				1201	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
				1202	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
				1203	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1204	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
				1205
				1206	These are forwarding methods that make it easy to access the contents of a
				1207	<tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1208	list.<p>
				1209
				1210	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
				1211
				1212	Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
				1213	neccesary to use when you need to update the list or perform a complex action
				1214	that doesn't have a forwarding method.<p>
				1215
				1216
				1217	<li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
				1218	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
				1219	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1220	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt><p>
				1221
				1222	These are forwarding methods that make it easy to access the contents of a
				1223	<tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a> list.<p>
				1224
				1225	<li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
				1226
				1227	Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1228	neccesary to use when you need to update the list or perform a complex action
				1229	that doesn't have a forwarding method.<p>
				1230
				1231
				1232
				1233	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
				1234
				1235	Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1236	function. Because the entry block for the function is always the first block,
				1237	this returns the first block of the <tt>Function</tt>.<p>
				1238
				1239	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1240	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
				1241
				1242	This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
				1243	and returns the return type of the function, or the <a
				1244	href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
				1245
				1246
				1247	<li><tt>bool hasSymbolTable() const</tt><p>
				1248
				1249	Return true if the <tt>Function</tt> has a symbol table allocated to it and if
				1250	there is at least one entry in it.<p>
				1251
				1252	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
				1253
				1254	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1255	<tt>Function</tt> or a null pointer if one has not been allocated (because there
				1256	are no named values in the function).<p>
				1257
				1258	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
				1259
				1260	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1261	<tt>Function</tt> or allocate a new <a
				1262	href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
				1263	should only be used when adding elements to the <a
				1264	href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
				1265	not left laying around.<p>
				1266
				1267
				1268
				1269	<!-- ======================================================================= -->
				1270	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1271	<tr><td> </td><td width="100%">
				1272	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1273	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1274	</b></font></td></tr></table><ul>
				1275
				1276	<tt>#include "<a
				1277	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
				1278	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
				1279	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1280	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
				1281
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1282	Global variables are represented with the (suprise suprise)
				1283	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
				1284	also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
				1285	are always referenced by their address (global values must live in memory, so
				1286	their "name" refers to their address). Global variables may have an initial
				1287	value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
				1288	have an initializer, they may be marked as "constant" themselves (indicating
				1289	that their contents never change at runtime).<p>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1290
				1291
				1292	<!-- _______________________________________________________________________ -->
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1293	</ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
				1294	<tt>GlobalVariable</tt> class</h4><ul>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1295
				1296	<li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
				1297	isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
				1298	&Name = "")</tt><p>
				1299
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1300	Create a new global variable of the specified type. If <tt>isConstant</tt> is
				1301	true then the global variable will be marked as unchanging for the program, and
				1302	if <tt>isInternal</tt> is true the resultant global variable will have internal
				1303	linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
				1304
				1305
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1306	<li><tt>bool isConstant() const</tt><p>
				1307
				1308	Returns true if this is a global variable is known not to be modified at
				1309	runtime.<p>
				1310
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1311
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1312	<li><tt>bool hasInitializer()</tt><p>
				1313
				1314	Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
				1315
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1316
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1317	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
				1318
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1319	Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
				1320	this method if there is no initializer.<p>
				1321
				1322
				1323	<!-- ======================================================================= -->
				1324	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1325	<tr><td> </td><td width="100%">
				1326	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1327	<a name="Module">The <tt>Module</tt> class</a>
				1328	</b></font></td></tr></table><ul>
				1329
				1330	<tt>#include "<a
				1331	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
				1332	doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
				1333
				1334	The <tt>Module</tt> class represents the top level structure present in LLVM
				1335	programs. An LLVM module is effectively either a translation unit of the
				1336	original program or a combination of several translation units merged by the
				1337	linker. The <tt>Module</tt> class keeps track of a list of <a
				1338	href="#Function"><tt>Function</tt></a>s, a list of <a
				1339	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1340	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1341	helpful member functions that try to make common operations easy.<p>
				1342
				1343
				1344	<!-- _______________________________________________________________________ -->
				1345	</ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
				1346	<tt>Module</tt> class</h4><ul>
				1347
				1348	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
				1349	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
				1350	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1351	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
				1352
				1353	These are forwarding methods that make it easy to access the contents of a
				1354	<tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1355	list.<p>
				1356
				1357	<li><tt>Module::FunctionListType &getFunctionList()</tt><p>
				1358
				1359	Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1360	neccesary to use when you need to update the list or perform a complex action
				1361	that doesn't have a forwarding method.<p>
				1362
				1363	<!-- Global Variable -->
				1364	<hr size=0>
				1365
				1366	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1367	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1368	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1369	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
				1370
				1371	These are forwarding methods that make it easy to access the contents of a
				1372	<tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
				1373	list.<p>
				1374
				1375	<li><tt>Module::GlobalListType &getGlobalList()</tt><p>
				1376
				1377	Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
				1378	This is neccesary to use when you need to update the list or perform a complex
				1379	action that doesn't have a forwarding method.<p>
				1380
				1381
				1382	<!-- Symbol table stuff -->
				1383	<hr size=0>
				1384
				1385	<li><tt>bool hasSymbolTable() const</tt><p>
				1386
				1387	Return true if the <tt>Module</tt> has a symbol table allocated to it and if
				1388	there is at least one entry in it.<p>
				1389
				1390	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
				1391
				1392	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1393	<tt>Module</tt> or a null pointer if one has not been allocated (because there
				1394	are no named values in the function).<p>
				1395
				1396	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
				1397
				1398	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1399	<tt>Module</tt> or allocate a new <a
				1400	href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
				1401	should only be used when adding elements to the <a
				1402	href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
				1403	not left laying around.<p>
				1404
				1405
				1406	<!-- Convenience methods -->
				1407	<hr size=0>
				1408
				1409	<li><tt><a href="#Function">Function</a> getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> Ty)</tt><p>
				1410
				1411	Look up the specified function in the <tt>Module</tt> <a
				1412	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1413	<tt>null</tt>.<p>
				1414
				1415
				1416	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
				1417	&Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
				1418
				1419	Look up the specified function in the <tt>Module</tt> <a
				1420	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1421	external declaration for the function and return it.<p>
				1422
				1423
				1424	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
				1425
				1426	If there is at least one entry in the <a
				1427	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1428	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1429	string.<p>
				1430
				1431
				1432	<li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
				1433	*Ty)</tt><p>
				1434
				1435	Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
				1436	<tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
				1437	is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
				1438	modified.<p>
				1439
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1440
				1441	<!-- ======================================================================= -->
				1442	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1443	<tr><td> </td><td width="100%">
				1444	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1445	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1446	</b></font></td></tr></table><ul>
				1447
				1448	Constant represents a base class for different types of constants. It is
				1449	subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1450	ConstantArray etc for representing the various types of Constants.<p>
				1451
				1452
				1453	<!-- _______________________________________________________________________ -->
				1454	</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
				1455
				1456	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
				1457
				1458
				1459
				1460
				1461	\subsection{Important Subclasses of Constant}
				1462	\begin{itemize}
				1463	<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
				1464	\begin{itemize}
				1465	<li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
				1466	\end{itemize}
				1467	<li>ConstantUInt : This class represents an unsigned integer.
				1468	\begin{itemize}
				1469	<li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
				1470	\end{itemize}
				1471	<li>ConstantFP : This class represents a floating point constant.
				1472	\begin{itemize}
				1473	<li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
				1474	\end{itemize}
				1475	<li>ConstantBool : This represents a boolean constant.
				1476	\begin{itemize}
				1477	<li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
				1478	\end{itemize}
				1479	<li>ConstantArray : This represents a constant array.
				1480	\begin{itemize}
				1481	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
				1482	\end{itemize}
				1483	<li>ConstantStruct : This represents a constant struct.
				1484	\begin{itemize}
				1485	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
				1486	\end{itemize}
				1487	<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
				1488	\begin{itemize}
				1489	<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
				1490	\end{itemize}
				1491	\end{itemize}
				1492
				1493
				1494	<!-- ======================================================================= -->
				1495	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1496	<tr><td> </td><td width="100%">
				1497	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1498	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1499	</b></font></td></tr></table><ul>
				1500
				1501	Type as noted earlier is also a subclass of a Value class. Any primitive
				1502	type (like int, short etc) in LLVM is an instance of Type Class. All
				1503	other types are instances of subclasses of type like FunctionType,
				1504	ArrayType etc. DerivedType is the interface for all such dervied types
				1505	including FunctionType, ArrayType, PointerType, StructType. Types can have
				1506	names. They can be recursive (StructType). There exists exactly one instance
				1507	of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
				1508
				1509	<!-- _______________________________________________________________________ -->
				1510	</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
				1511
				1512	<li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
				1513	<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.
				1514	<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.
				1515	<li><tt> bool isInteger () const</tt>: Equilivent to isSigned() \|\| isUnsigned(), but with only a single virtual function invocation.
				1516	<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.
				1517
				1518	<li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
				1519	<li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
				1520	<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.
				1521	<li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
				1522	<li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
				1523	<li><tt>const Type * getContainedType (unsigned i) const</tt>:
				1524	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.
				1525	<li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
				1526
				1527
				1528
				1529	\subsection{Derived Types}
				1530	\begin{itemize}
				1531	<li>SequentialType : This is subclassed by ArrayType and PointerType
				1532	\begin{itemize}
				1533	<li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
				1534	\end{itemize}
				1535	<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
				1536	\begin{itemize}
				1537	<li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
				1538	\end{itemize}
				1539	<li>PointerType : Subclass of SequentialType for pointer types.
				1540	<li>StructType : subclass of DerivedTypes for struct types
				1541	<li>FunctionType : subclass of DerivedTypes for function types.
				1542	\begin{itemize}
				1543
				1544	<li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
				1545	<li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
				1546	<li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
				1547	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
				1548	<li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
				1549	\end{itemize}
				1550	\end{itemize}
				1551
				1552
				1553
				1554
				1555	<!-- ======================================================================= -->
				1556	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1557	<tr><td> </td><td width="100%">
				1558	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1559	<a name="Argument">The <tt>Argument</tt> class</a>
				1560	</b></font></td></tr></table><ul>
				1561
				1562	This subclass of Value defines the interface for incoming formal arguments to a
				1563	function. A Function maitanis a list of its formal arguments. An argument has a
				1564	pointer to the parent Function.
				1565
				1566
				1567
				1568
				1569	<!-- *********************************************************************** -->
				1570	</ul>
				1571	<!-- *********************************************************************** -->
				1572
				1573	<hr><font size-1>
				1574	<address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				1575	<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
				1576	<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
				1577	<!-- hhmts start -->
Chris Lattner	4e1f96b	2002-09-12 19:06:51 +0000	[diff] [blame^]	1578	Last modified: Thu Sep 12 14:06:40 CDT 2002
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1579	<!-- hhmts end -->
				1580	</font></body></html>