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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
				623	the <a href="/doxygen/classInstruction.h">doxygen documentation for
				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
				704	<tt>Instruction</tt>s</h4><ul>
				705
				706	<!--_______________________________________________________________________-->
				707	</ul><h4><a name="schanges_replacing"><hr size=0>Replacing an
				708	<tt>Instruction</tt> with another <tt>Value</tt></h4><ul>
				709
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	710	<!-- Value::replaceAllUsesWith
				711	User::replaceUsesOfWith
				712	Point out: include/llvm/Transforms/Utils/
				713	especially BasicBlockUtils.h with:
				714	ReplaceInstWithValue, ReplaceInstWithInst
				715
				716	-->
Chris Lattner	b99344f	2002-09-06 16:40:10 +0000	[diff] [blame]	717
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	718	<!-- *********************************************************************** -->
				719	</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
				720	<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]	721	<a name="coreclasses">The Core LLVM Class Hierarchy Reference
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	722	</b></font></td></tr></table><ul>
				723	<!-- *********************************************************************** -->
				724
				725	The Core LLVM classes are the primary means of representing the program being
				726	inspected or transformed. The core LLVM classes are defined in header files in
				727	the <tt>include/llvm/</tt> directory, and implemented in the <tt>lib/VMCore</tt>
				728	directory.<p>
				729
				730
				731	<!-- ======================================================================= -->
				732	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				733	<tr><td> </td><td width="100%">
				734	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				735	<a name="Value">The <tt>Value</tt> class</a>
				736	</b></font></td></tr></table><ul>
				737
				738	<tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt></b><br>
				739	doxygen info: <a href="/doxygen/classValue.html">Value Class</a><p>
				740
				741
				742	The <tt>Value</tt> class is the most important class in LLVM Source base. It
				743	represents a typed value that may be used (among other things) as an operand to
				744	an instruction. There are many different types of <tt>Value</tt>s, such as <a
				745	href="#Constant"><tt>Constant</tt></a>s, <a
				746	href="#Argument"><tt>Argument</tt></a>s, and even <a
				747	href="#Instruction"><tt>Instruction</tt></a>s and <a
				748	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.<p>
				749
				750	A particular <tt>Value</tt> may be used many times in the LLVM representation
				751	for a program. For example, an incoming argument to a function (represented
				752	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				753	every instruction in the function that references the argument. To keep track
				754	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				755	href="#User"><tt>User</tt></a>s that is using it (the <a
				756	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				757	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]	758	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]	759	methods, shown below.<p>
				760
				761	Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed, and
				762	this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				763	method. <a name="#nameWarning">In addition, all LLVM values can be named. The
				764	"name" of the <tt>Value</tt> is symbolic string printed in the LLVM code:<p>
				765
				766	<pre>
				767	%<b>foo</b> = add int 1, 2
				768	</pre>
				769
				770	The name of this instruction is "foo". <b>NOTE</b> that the name of any value
				771	may be missing (an empty string), so names should <b>ONLY</b> be used for
				772	debugging (making the source code easier to read, debugging printouts), they
				773	should not be used to keep track of values or map between them. For this
				774	purpose, use a <tt>std::map</tt> of pointers to the <tt>Value</tt> itself
				775	instead.<p>
				776
				777	One important aspect of LLVM is that there is no distinction between an SSA
				778	variable and the operation that produces it. Because of this, any reference to
				779	the value produced by an instruction (or the value available as an incoming
				780	argument, for example) is represented as a direct pointer to the class that
				781	represents this value. Although this may take some getting used to, it
				782	simplifies the representation and makes it easier to manipulate.<p>
				783
				784
				785	<!-- _______________________________________________________________________ -->
				786	</ul><h4><a name="m_Value"><hr size=0>Important Public Members of
				787	the <tt>Value</tt> class</h4><ul>
				788
				789	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the use-list<br>
				790	<tt>Value::use_const_iterator</tt>
				791	- Typedef for const_iterator over the use-list<br>
				792	<tt>unsigned use_size()</tt> - Returns the number of users of the value.<br>
				793	<tt>bool use_empty()</tt> - Returns true if there are no users.<br>
				794	<tt>use_iterator use_begin()</tt>
				795	- Get an iterator to the start of the use-list.<br>
				796	<tt>use_iterator use_end()</tt>
				797	- Get an iterator to the end of the use-list.<br>
				798	<tt><a href="#User">User</a> *use_back()</tt>
				799	- Returns the last element in the list.<p>
				800
				801	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>
				802
				803	<li><tt><a href="#Type">Type</a> *getType() const</tt><p>
				804	This method returns the Type of the Value.
				805
				806	<li><tt>bool hasName() const</tt><br>
				807	<tt>std::string getName() const</tt><br>
				808	<tt>void setName(const std::string &Name)</tt><p>
				809
				810	This family of methods is used to access and assign a name to a <tt>Value</tt>,
				811	be aware of the <a href="#nameWarning">precaution above</a>.<p>
				812
				813
				814	<li><tt>void replaceAllUsesWith(Value *V)</tt><p>
				815
				816	This method traverses the use list of a <tt>Value</tt> changing all <a
				817	href="#User"><tt>User</tt>'s</a> of the current value to refer to "<tt>V</tt>"
				818	instead. For example, if you detect that an instruction always produces a
				819	constant value (for example through constant folding), you can replace all uses
				820	of the instruction with the constant like this:<p>
				821
				822	<pre>
				823	Inst->replaceAllUsesWith(ConstVal);
				824	</pre><p>
				825
				826
				827
				828	<!-- ======================================================================= -->
				829	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				830	<tr><td> </td><td width="100%">
				831	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				832	<a name="User">The <tt>User</tt> class</a>
				833	</b></font></td></tr></table><ul>
				834
				835	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt></b><br>
				836	doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
				837	Superclass: <a href="#Value"><tt>Value</tt></a><p>
				838
				839
				840	The <tt>User</tt> class is the common base class of all LLVM nodes that may
				841	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				842	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				843	referring to. The <tt>User</tt> class itself is a subclass of
				844	<tt>Value</tt>.<p>
				845
				846	The operands of a <tt>User</tt> point directly to the LLVM <a
				847	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				848	Single Assignment (SSA) form, there can only be one definition referred to,
				849	allowing this direct connection. This connection provides the use-def
				850	information in LLVM.<p>
				851
				852	<!-- _______________________________________________________________________ -->
				853	</ul><h4><a name="m_User"><hr size=0>Important Public Members of
				854	the <tt>User</tt> class</h4><ul>
				855
				856	The <tt>User</tt> class exposes the operand list in two ways: through an index
				857	access interface and through an iterator based interface.<p>
				858
				859	<li><tt>Value *getOperand(unsigned i)</tt><br>
				860	<tt>unsigned getNumOperands()</tt><p>
				861
				862	These two methods expose the operands of the <tt>User</tt> in a convenient form
				863	for direct access.<p>
				864
				865	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand list<br>
				866	<tt>User::op_const_iterator</tt>
				867	<tt>use_iterator op_begin()</tt>
				868	- Get an iterator to the start of the operand list.<br>
				869	<tt>use_iterator op_end()</tt>
				870	- Get an iterator to the end of the operand list.<p>
				871
				872	Together, these methods make up the iterator based interface to the operands of
				873	a <tt>User</tt>.<p>
				874
				875
				876
				877	<!-- ======================================================================= -->
				878	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				879	<tr><td> </td><td width="100%">
				880	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				881	<a name="Instruction">The <tt>Instruction</tt> class</a>
				882	</b></font></td></tr></table><ul>
				883
				884	<tt>#include "<a
				885	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt></b><br>
				886	doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
				887	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				888	href="#Value"><tt>Value</tt></a><p>
				889
				890	The <tt>Instruction</tt> class is the common base class for all LLVM
				891	instructions. It provides only a few methods, but is a very commonly used
				892	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				893	opcode (instruction type) and the parent <a
				894	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				895	into. To represent a specific type of instruction, one of many subclasses of
				896	<tt>Instruction</tt> are used.<p>
				897
				898	Because the <tt>Instruction</tt> class subclasses the <a
				899	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				900	way as for other <a href="#User"><tt>User</tt></a>s (with the
				901	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				902	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).<p>
				903
Chris Lattner	1763525	2002-09-12 17:18:46 +0000	[diff] [blame]	904	An important file for the <tt>Instruction</tt> class is the
				905	<tt>llvm/Instruction.def</tt> file. This file contains some meta-data about the
				906	various different types of instructions in LLVM. It describes the enum values
				907	that are used as opcodes (for example <tt>Instruction::Add</tt> and
				908	<tt>Instruction::SetLE</tt>), as well as the concrete sub-classes of
				909	<tt>Instruction</tt> that implement the instruction (for example <tt><a
				910	href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				911	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				912	this file confused doxygen, so these enum values don't show up correctly in the
				913	<a href="/doxygen/classInstruction.html">doxygen output</a>.<p>
				914
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	915
				916	<!-- _______________________________________________________________________ -->
				917	</ul><h4><a name="m_Instruction"><hr size=0>Important Public Members of
				918	the <tt>Instruction</tt> class</h4><ul>
				919
				920	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt><p>
				921
				922	Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that this
				923	<tt>Instruction</tt> is embedded into.<p>
				924
				925	<li><tt>bool hasSideEffects()</tt><p>
				926
				927	Returns true if the instruction has side effects, i.e. it is a <tt>call</tt>,
				928	<tt>free</tt>, <tt>invoke</tt>, or <tt>store</tt>.<p>
				929
				930	<li><tt>unsigned getOpcode()</tt><p>
				931
				932	Returns the opcode for the <tt>Instruction</tt>.<p>
				933
Chris Lattner	1763525	2002-09-12 17:18:46 +0000	[diff] [blame]	934	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt><p>
				935
				936	Returns another instance of the specified instruction, identical in all ways to
				937	the original except that the instruction has no parent (ie it's not embedded
				938	into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>), and it has no name.<p>
				939
				940
				941
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	942	<!--
				943
				944	\subsection{Subclasses of Instruction :}
				945	\begin{itemize}
				946	<li>BinaryOperator : This subclass of Instruction defines a general interface to the all the instructions involvong binary operators in LLVM.
				947	\begin{itemize}
				948	<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.
				949	\end{itemize}
				950	<li>TerminatorInst : This subclass of Instructions defines an interface for all instructions that can terminate a BasicBlock.
				951	\begin{itemize}
				952	<li> <tt>unsigned getNumSuccessors()</tt>: Returns the number of successors for this terminator instruction.
				953	<li><tt>BasicBlock *getSuccessor(unsigned i)</tt>: As the name suggests returns the ith successor BasicBlock.
				954	<li><tt>void setSuccessor(unsigned i, BasicBlock *B)</tt>: sets BasicBlock B as the ith succesor to this terminator instruction.
				955	\end{itemize}
				956
				957	<li>PHINode : This represents the PHI instructions in the SSA form.
				958	\begin{itemize}
				959	<li><tt> unsigned getNumIncomingValues()</tt>: Returns the number of incoming edges to this PHI node.
				960	<li><tt> Value *getIncomingValue(unsigned i)</tt>: Returns the ith incoming Value.
				961	<li><tt>void setIncomingValue(unsigned i, Value *V)</tt>: Sets the ith incoming Value as V
				962	<li><tt>BasicBlock *getIncomingBlock(unsigned i)</tt>: Returns the Basic Block corresponding to the ith incoming Value.
				963	<li><tt> void addIncoming(Value D, BasicBlock BB)</tt>:
				964	Add an incoming value to the end of the PHI list
				965	<li><tt> int getBasicBlockIndex(const BasicBlock *BB) const</tt>:
				966	Returns the first index of the specified basic block in the value list for this PHI. Returns -1 if no instance.
				967	\end{itemize}
				968	<li>CastInst : In LLVM all casts have to be done through explicit cast instructions. CastInst defines the interface to the cast instructions.
				969	<li>CallInst : This defines an interface to the call instruction in LLVM. ARguments to the function are nothing but operands of the instruction.
				970	\begin{itemize}
				971	<li>: <tt>Function *getCalledFunction()</tt>: Returns a handle to the function that is being called by this Function.
				972	\end{itemize}
				973	<li>LoadInst, StoreInst, GetElemPtrInst : These subclasses represent load, store and getelementptr instructions in LLVM.
				974	\begin{itemize}
				975	<li><tt>Value * getPointerOperand ()</tt>: Returns the Pointer Operand which is typically the 0th operand.
				976	\end{itemize}
				977	<li>BranchInst : This is a subclass of TerminatorInst and defines the interface for conditional and unconditional branches in LLVM.
				978	\begin{itemize}
				979	<li><tt>bool isConditional()</tt>: Returns true if the branch is a conditional branch else returns false
				980	<li> <tt>Value *getCondition()</tt>: Returns the condition if it is a conditional branch else returns null.
				981	<li> <tt>void setUnconditionalDest(BasicBlock *Dest)</tt>: Changes the current branch to an unconditional one targetting the specified block.
				982	\end{itemize}
				983
				984	\end{itemize}
				985
				986	-->
				987
				988
				989	<!-- ======================================================================= -->
				990	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				991	<tr><td> </td><td width="100%">
				992	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				993	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				994	</b></font></td></tr></table><ul>
				995
				996	<tt>#include "<a
				997	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt></b><br>
				998	doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
				999	Superclass: <a href="#Value"><tt>Value</tt></a><p>
				1000
				1001
				1002	This class represents a single entry multiple exit section of the code, commonly
				1003	known as a basic block by the compiler community. The <tt>BasicBlock</tt> class
				1004	maintains a list of <a href="#Instruction"><tt>Instruction</tt></a>s, which form
				1005	the body of the block. Matching the language definition, the last element of
				1006	this list of instructions is always a terminator instruction (a subclass of the
				1007	<a href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).<p>
				1008
				1009	In addition to tracking the list of instructions that make up the block, the
				1010	<tt>BasicBlock</tt> class also keeps track of the <a
				1011	href="#Function"><tt>Function</tt></a> that it is embedded into.<p>
				1012
				1013	Note that <tt>BasicBlock</tt>s themselves are <a
				1014	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1015	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1016	<tt>label</tt>.<p>
				1017
				1018
				1019	<!-- _______________________________________________________________________ -->
				1020	</ul><h4><a name="m_BasicBlock"><hr size=0>Important Public Members of
				1021	the <tt>BasicBlock</tt> class</h4><ul>
				1022
				1023	<li><tt>BasicBlock(const std::string &Name = "", <a
				1024	href="#Function">Function</a> *Parent = 0)</tt><p>
				1025
				1026	The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1027	insertion into a function. The constructor simply takes a name for the new
				1028	block, and optionally a <a href="#Function"><tt>Function</tt></a> to insert it
				1029	into. If the <tt>Parent</tt> parameter is specified, the new
				1030	<tt>BasicBlock</tt> is automatically inserted at the end of the specified <a
				1031	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1032	manually inserted into the <a href="#Function"><tt>Function</tt></a>.<p>
				1033
				1034	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1035	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1036	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1037	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
				1038
				1039	These methods and typedefs are forwarding functions that have the same semantics
				1040	as the standard library methods of the same names. These methods expose the
				1041	underlying instruction list of a basic block in a way that is easy to
				1042	manipulate. To get the full complement of container operations (including
				1043	operations to update the list), you must use the <tt>getInstList()</tt>
				1044	method.<p>
				1045
				1046	<li><tt>BasicBlock::InstListType &getInstList()</tt><p>
				1047
				1048	This method is used to get access to the underlying container that actually
				1049	holds the Instructions. This method must be used when there isn't a forwarding
				1050	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1051	to perform. Because there are no forwarding functions for "updating"
				1052	operations, you need to use this if you want to update the contents of a
				1053	<tt>BasicBlock</tt>.<p>
				1054
				1055	<li><tt><A href="#Function">Function</a> *getParent()</tt><p>
				1056
				1057	Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1058	embedded into, or a null pointer if it is homeless.<p>
				1059
				1060	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt><p>
				1061
				1062	Returns a pointer to the terminator instruction that appears at the end of the
				1063	<tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1064	instruction in the block is not a terminator, then a null pointer is
				1065	returned.<p>
				1066
				1067
				1068	<!-- ======================================================================= -->
				1069	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1070	<tr><td> </td><td width="100%">
				1071	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1072	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1073	</b></font></td></tr></table><ul>
				1074
				1075	<tt>#include "<a
				1076	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt></b><br>
				1077	doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
				1078	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1079	href="#Value"><tt>Value</tt></a><p>
				1080
				1081	Global values (<A href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1082	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1083	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1084	Because they are visible at global scope, they are also subject to linking with
				1085	other globals defined in different translation units. To control the linking
				1086	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1087	<tt>GlobalValue</tt>s know whether they have internal or external linkage.<p>
				1088
				1089	If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1090	<tt>static</tt> in C), it is not visible to code outside the current translation
				1091	unit, and does not participate in linking. If it has external linkage, it is
				1092	visible to external code, and does participate in linking. In addition to
				1093	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1094	href="#Module"><tt>Module</tt></a> they are currently part of.<p>
				1095
				1096	Because <tt>GlobalValue</tt>s are memory objects, they are always referred to by
				1097	their address. As such, the <a href="#Type"><tt>Type</tt></a> of a global is
				1098	always a pointer to its contents. This is explained in the LLVM Language
				1099	Reference Manual.<p>
				1100
				1101
				1102	<!-- _______________________________________________________________________ -->
				1103	</ul><h4><a name="m_GlobalValue"><hr size=0>Important Public Members of
				1104	the <tt>GlobalValue</tt> class</h4><ul>
				1105
				1106	<li><tt>bool hasInternalLinkage() const</tt><br>
				1107	<tt>bool hasExternalLinkage() const</tt><br>
				1108	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt><p>
				1109
				1110	These methods manipulate the linkage characteristics of the
				1111	<tt>GlobalValue</tt>.<p>
				1112
				1113	<li><tt><a href="#Module">Module</a> *getParent()</tt><p>
				1114
				1115	This returns the <a href="#Module"><tt>Module</tt></a> that the GlobalValue is
				1116	currently embedded into.<p>
				1117
				1118
				1119
				1120	<!-- ======================================================================= -->
				1121	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1122	<tr><td> </td><td width="100%">
				1123	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1124	<a name="Function">The <tt>Function</tt> class</a>
				1125	</b></font></td></tr></table><ul>
				1126
				1127	<tt>#include "<a
				1128	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt></b><br>
				1129	doxygen info: <a href="/doxygen/classFunction.html">Function Class</a><br>
				1130	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1131	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
				1132
				1133	The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1134	actually one of the more complex classes in the LLVM heirarchy because it must
				1135	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1136	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1137	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1138	href="#SymbolTable"><tt>SymbolTable</tt></a>.<p>
				1139
				1140	The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most commonly
				1141	used part of <tt>Function</tt> objects. The list imposes an implicit ordering
				1142	of the blocks in the function, which indicate how the code will be layed out by
				1143	the backend. Additionally, the first <a
				1144	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1145	<tt>Function</tt>. It is not legal in LLVM explicitly branch to this initial
				1146	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1147	nodes from a single <tt>Function</tt>. If the <a
				1148	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1149	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1150	function hasn't been linked in yet.<p>
				1151
				1152	In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1153	<tt>Function</tt> class also keeps track of the list of formal <a
				1154	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1155	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1156	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1157	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.<p>
				1158
				1159	The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used LLVM
				1160	feature that is only used when you have to look up a value by name. Aside from
				1161	that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used internally to
				1162	make sure that there are not conflicts between the names of <a
				1163	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1164	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1165	href="#Argument"><tt>Argument</tt></a>s in the function body.<p>
				1166
				1167
				1168	<!-- _______________________________________________________________________ -->
				1169	</ul><h4><a name="m_Function"><hr size=0>Important Public Members of
				1170	the <tt>Function</tt> class</h4><ul>
				1171
				1172	<li><tt>Function(const <a href="#FunctionType">FunctionType</a> *Ty, bool isInternal, const std::string &N = "")</tt><p>
				1173
				1174	Constructor used when you need to create new <tt>Function</tt>s to add the the
				1175	program. The constructor must specify the type of the function to create and
				1176	whether or not it should start out with internal or external linkage.<p>
				1177
				1178	<li><tt>bool isExternal()</tt><p>
				1179
				1180	Return whether or not the <tt>Function</tt> has a body defined. If the function
				1181	is "external", it does not have a body, and thus must be resolved by linking
				1182	with a function defined in a different translation unit.<p>
				1183
				1184
				1185	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
				1186	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
				1187	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1188	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
				1189
				1190	These are forwarding methods that make it easy to access the contents of a
				1191	<tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1192	list.<p>
				1193
				1194	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt><p>
				1195
				1196	Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This is
				1197	neccesary to use when you need to update the list or perform a complex action
				1198	that doesn't have a forwarding method.<p>
				1199
				1200
				1201	<li><tt>Function::aiterator</tt> - Typedef for the argument list iterator<br>
				1202	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
				1203	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1204	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</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="#Argument"><tt>Argument</tt></a> list.<p>
				1208
				1209	<li><tt>Function::ArgumentListType &getArgumentList()</tt><p>
				1210
				1211	Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1212	neccesary to use when you need to update the list or perform a complex action
				1213	that doesn't have a forwarding method.<p>
				1214
				1215
				1216
				1217	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryNode()</tt><p>
				1218
				1219	Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1220	function. Because the entry block for the function is always the first block,
				1221	this returns the first block of the <tt>Function</tt>.<p>
				1222
				1223	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1224	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt><p>
				1225
				1226	This traverses the <a href="#Type"><tt>Type</tt></a> of the <tt>Function</tt>
				1227	and returns the return type of the function, or the <a
				1228	href="#FunctionType"><tt>FunctionType</tt></a> of the actual function.<p>
				1229
				1230
				1231	<li><tt>bool hasSymbolTable() const</tt><p>
				1232
				1233	Return true if the <tt>Function</tt> has a symbol table allocated to it and if
				1234	there is at least one entry in it.<p>
				1235
				1236	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
				1237
				1238	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1239	<tt>Function</tt> or a null pointer if one has not been allocated (because there
				1240	are no named values in the function).<p>
				1241
				1242	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
				1243
				1244	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1245	<tt>Function</tt> or allocate a new <a
				1246	href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
				1247	should only be used when adding elements to the <a
				1248	href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
				1249	not left laying around.<p>
				1250
				1251
				1252
				1253	<!-- ======================================================================= -->
				1254	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1255	<tr><td> </td><td width="100%">
				1256	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1257	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1258	</b></font></td></tr></table><ul>
				1259
				1260	<tt>#include "<a
				1261	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt></b><br>
				1262	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable Class</a><br>
				1263	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1264	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a><p>
				1265
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1266	Global variables are represented with the (suprise suprise)
				1267	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are
				1268	also subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such
				1269	are always referenced by their address (global values must live in memory, so
				1270	their "name" refers to their address). Global variables may have an initial
				1271	value (which must be a <a href="#Constant"><tt>Constant</tt></a>), and if they
				1272	have an initializer, they may be marked as "constant" themselves (indicating
				1273	that their contents never change at runtime).<p>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1274
				1275
				1276	<!-- _______________________________________________________________________ -->
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1277	</ul><h4><a name="m_GlobalVariable"><hr size=0>Important Public Members of the
				1278	<tt>GlobalVariable</tt> class</h4><ul>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1279
				1280	<li><tt>GlobalVariable(const <a href="#Type">Type</a> *Ty, bool isConstant, bool
				1281	isInternal, <a href="#Constant">Constant</a> *Initializer = 0, const std::string
				1282	&Name = "")</tt><p>
				1283
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1284	Create a new global variable of the specified type. If <tt>isConstant</tt> is
				1285	true then the global variable will be marked as unchanging for the program, and
				1286	if <tt>isInternal</tt> is true the resultant global variable will have internal
				1287	linkage. Optionally an initializer and name may be specified for the global variable as well.<p>
				1288
				1289
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1290	<li><tt>bool isConstant() const</tt><p>
				1291
				1292	Returns true if this is a global variable is known not to be modified at
				1293	runtime.<p>
				1294
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1295
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1296	<li><tt>bool hasInitializer()</tt><p>
				1297
				1298	Returns true if this <tt>GlobalVariable</tt> has an intializer.<p>
				1299
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1300
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1301	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt><p>
				1302
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1303	Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal to call
				1304	this method if there is no initializer.<p>
				1305
				1306
				1307	<!-- ======================================================================= -->
				1308	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1309	<tr><td> </td><td width="100%">
				1310	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1311	<a name="Module">The <tt>Module</tt> class</a>
				1312	</b></font></td></tr></table><ul>
				1313
				1314	<tt>#include "<a
				1315	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt></b><br>
				1316	doxygen info: <a href="/doxygen/classModule.html">Module Class</a><p>
				1317
				1318	The <tt>Module</tt> class represents the top level structure present in LLVM
				1319	programs. An LLVM module is effectively either a translation unit of the
				1320	original program or a combination of several translation units merged by the
				1321	linker. The <tt>Module</tt> class keeps track of a list of <a
				1322	href="#Function"><tt>Function</tt></a>s, a list of <a
				1323	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1324	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1325	helpful member functions that try to make common operations easy.<p>
				1326
				1327
				1328	<!-- _______________________________________________________________________ -->
				1329	</ul><h4><a name="m_Module"><hr size=0>Important Public Members of the
				1330	<tt>Module</tt> class</h4><ul>
				1331
				1332	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
				1333	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
				1334	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1335	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt><p>
				1336
				1337	These are forwarding methods that make it easy to access the contents of a
				1338	<tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1339	list.<p>
				1340
				1341	<li><tt>Module::FunctionListType &getFunctionList()</tt><p>
				1342
				1343	Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1344	neccesary to use when you need to update the list or perform a complex action
				1345	that doesn't have a forwarding method.<p>
				1346
				1347	<!-- Global Variable -->
				1348	<hr size=0>
				1349
				1350	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1351	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1352	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1353	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt><p>
				1354
				1355	These are forwarding methods that make it easy to access the contents of a
				1356	<tt>Module</tt> object's <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>
				1357	list.<p>
				1358
				1359	<li><tt>Module::GlobalListType &getGlobalList()</tt><p>
				1360
				1361	Returns the list of <a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s.
				1362	This is neccesary to use when you need to update the list or perform a complex
				1363	action that doesn't have a forwarding method.<p>
				1364
				1365
				1366	<!-- Symbol table stuff -->
				1367	<hr size=0>
				1368
				1369	<li><tt>bool hasSymbolTable() const</tt><p>
				1370
				1371	Return true if the <tt>Module</tt> has a symbol table allocated to it and if
				1372	there is at least one entry in it.<p>
				1373
				1374	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt><p>
				1375
				1376	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1377	<tt>Module</tt> or a null pointer if one has not been allocated (because there
				1378	are no named values in the function).<p>
				1379
				1380	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTableSure()</tt><p>
				1381
				1382	Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a> for this
				1383	<tt>Module</tt> or allocate a new <a
				1384	href="#SymbolTable"><tt>SymbolTable</tt></a> if one is not already around. This
				1385	should only be used when adding elements to the <a
				1386	href="#SymbolTable"><tt>SymbolTable</tt></a>, so that empty symbol tables are
				1387	not left laying around.<p>
				1388
				1389
				1390	<!-- Convenience methods -->
				1391	<hr size=0>
				1392
				1393	<li><tt><a href="#Function">Function</a> getFunction(const std::string &Name, const <a href="#FunctionType">FunctionType</a> Ty)</tt><p>
				1394
				1395	Look up the specified function in the <tt>Module</tt> <a
				1396	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1397	<tt>null</tt>.<p>
				1398
				1399
				1400	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const std::string
				1401	&Name, const <a href="#FunctionType">FunctionType</a> *T)</tt><p>
				1402
				1403	Look up the specified function in the <tt>Module</tt> <a
				1404	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1405	external declaration for the function and return it.<p>
				1406
				1407
				1408	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt><p>
				1409
				1410	If there is at least one entry in the <a
				1411	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1412	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1413	string.<p>
				1414
				1415
				1416	<li><tt>bool addTypeName(const std::string &Name, const <a href="#Type">Type</a>
				1417	*Ty)</tt><p>
				1418
				1419	Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a> mapping
				1420	<tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this name, true
				1421	is returned and the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is not
				1422	modified.<p>
				1423
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1424
				1425	<!-- ======================================================================= -->
				1426	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1427	<tr><td> </td><td width="100%">
				1428	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1429	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1430	</b></font></td></tr></table><ul>
				1431
				1432	Constant represents a base class for different types of constants. It is
				1433	subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1434	ConstantArray etc for representing the various types of Constants.<p>
				1435
				1436
				1437	<!-- _______________________________________________________________________ -->
				1438	</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
				1439
				1440	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a ConstantExpr
				1441
				1442
				1443
				1444
				1445	\subsection{Important Subclasses of Constant}
				1446	\begin{itemize}
				1447	<li>ConstantSInt : This subclass of Constant represents a signed integer constant.
				1448	\begin{itemize}
				1449	<li><tt>int64_t getValue () const</tt>: Returns the underlying value of this constant.
				1450	\end{itemize}
				1451	<li>ConstantUInt : This class represents an unsigned integer.
				1452	\begin{itemize}
				1453	<li><tt>uint64_t getValue () const</tt>: Returns the underlying value of this constant.
				1454	\end{itemize}
				1455	<li>ConstantFP : This class represents a floating point constant.
				1456	\begin{itemize}
				1457	<li><tt>double getValue () const</tt>: Returns the underlying value of this constant.
				1458	\end{itemize}
				1459	<li>ConstantBool : This represents a boolean constant.
				1460	\begin{itemize}
				1461	<li><tt>bool getValue () const</tt>: Returns the underlying value of this constant.
				1462	\end{itemize}
				1463	<li>ConstantArray : This represents a constant array.
				1464	\begin{itemize}
				1465	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
				1466	\end{itemize}
				1467	<li>ConstantStruct : This represents a constant struct.
				1468	\begin{itemize}
				1469	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns a Vecotr of component constants that makeup this array.
				1470	\end{itemize}
				1471	<li>ConstantPointerRef : This represents a constant pointer value that is initialized to point to a global value, which lies at a constant fixed address.
				1472	\begin{itemize}
				1473	<li><tt>GlobalValue *getValue()</tt>: Returns the global value to which this pointer is pointing to.
				1474	\end{itemize}
				1475	\end{itemize}
				1476
				1477
				1478	<!-- ======================================================================= -->
				1479	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1480	<tr><td> </td><td width="100%">
				1481	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1482	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1483	</b></font></td></tr></table><ul>
				1484
				1485	Type as noted earlier is also a subclass of a Value class. Any primitive
				1486	type (like int, short etc) in LLVM is an instance of Type Class. All
				1487	other types are instances of subclasses of type like FunctionType,
				1488	ArrayType etc. DerivedType is the interface for all such dervied types
				1489	including FunctionType, ArrayType, PointerType, StructType. Types can have
				1490	names. They can be recursive (StructType). There exists exactly one instance
				1491	of any type structure at a time. This allows using pointer equality of Type *s for comparing types.
				1492
				1493	<!-- _______________________________________________________________________ -->
				1494	</ul><h4><a name="m_Value"><hr size=0>Important Public Methods</h4><ul>
				1495
				1496	<li><tt>PrimitiveID getPrimitiveID () const</tt>: Returns the base type of the type.
				1497	<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.
				1498	<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.
				1499	<li><tt> bool isInteger () const</tt>: Equilivent to isSigned() \|\| isUnsigned(), but with only a single virtual function invocation.
				1500	<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.
				1501
				1502	<li><tt>bool isFloatingPoint ()</tt>: Return true if this is one of the two floating point types.
				1503	<li><tt>bool isRecursive () const</tt>: Returns rue if the type graph contains a cycle.
				1504	<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.
				1505	<li><tt>bool isPrimitiveType () const</tt>: Returns true if it is a primitive type.
				1506	<li><tt>bool isDerivedType () const</tt>: Returns true if it is a derived type.
				1507	<li><tt>const Type * getContainedType (unsigned i) const</tt>:
				1508	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.
				1509	<li><tt>unsigned getNumContainedTypes () const</tt>: Return the number of types in the derived type.
				1510
				1511
				1512
				1513	\subsection{Derived Types}
				1514	\begin{itemize}
				1515	<li>SequentialType : This is subclassed by ArrayType and PointerType
				1516	\begin{itemize}
				1517	<li><tt>const Type * getElementType () const</tt>: Returns the type of each of the elements in the sequential type.
				1518	\end{itemize}
				1519	<li>ArrayType : This is a subclass of SequentialType and defines interface for array types.
				1520	\begin{itemize}
				1521	<li><tt>unsigned getNumElements () const</tt>: Returns the number of elements in the array.
				1522	\end{itemize}
				1523	<li>PointerType : Subclass of SequentialType for pointer types.
				1524	<li>StructType : subclass of DerivedTypes for struct types
				1525	<li>FunctionType : subclass of DerivedTypes for function types.
				1526	\begin{itemize}
				1527
				1528	<li><tt>bool isVarArg () const</tt>: Returns true if its a vararg function
				1529	<li><tt> const Type * getReturnType () const</tt>: Returns the return type of the function.
				1530	<li><tt> const ParamTypes &getParamTypes () const</tt>: Returns a vector of parameter types.
				1531	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns the type of the ith parameter.
				1532	<li><tt> const unsigned getNumParams () const</tt>: Returns the number of formal parameters.
				1533	\end{itemize}
				1534	\end{itemize}
				1535
				1536
				1537
				1538
				1539	<!-- ======================================================================= -->
				1540	</ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
				1541	<tr><td> </td><td width="100%">
				1542	<font color="#EEEEFF" face="Georgia,Palatino"><b>
				1543	<a name="Argument">The <tt>Argument</tt> class</a>
				1544	</b></font></td></tr></table><ul>
				1545
				1546	This subclass of Value defines the interface for incoming formal arguments to a
				1547	function. A Function maitanis a list of its formal arguments. An argument has a
				1548	pointer to the parent Function.
				1549
				1550
				1551
				1552
				1553	<!-- *********************************************************************** -->
				1554	</ul>
				1555	<!-- *********************************************************************** -->
				1556
				1557	<hr><font size-1>
				1558	<address>By: <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				1559	<a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
				1560	<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
				1561	<!-- hhmts start -->
Chris Lattner	1763525	2002-09-12 17:18:46 +0000	[diff] [blame]	1562	Last modified: Thu Sep 12 12:18:04 CDT 2002
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1563	<!-- hhmts end -->
				1564	</font></body></html>