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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
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Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	8	<body>
				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
				18	<li><a href="#stl">The C++ Standard Template Library</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	19	<li>The <tt>-time-passes</tt> option
				20	<li>How to use the LLVM Makefile system
				21	<li>How to write a regression test
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	22	--> </li>
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	23	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	24	</li>
				25	<li><a href="#apis">Important and useful LLVM APIs</a>
				26	<ul>
				27	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				28	and <tt>dyn_cast<></tt> templates</a> </li>
				29	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				30	option</a>
				31	<ul>
				32	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				33	and the <tt>-debug-only</tt> option</a> </li>
				34	</ul>
				35	</li>
				36	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				37	option</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	38	<li>The <tt>InstVisitor</tt> template
				39	<li>The general graph API
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	40	--> </li>
				41	</ul>
				42	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	43	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	44	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	45	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				46	<ul>
				47	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				48	in a <tt>Function</tt></a> </li>
				49	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				50	in a <tt>BasicBlock</tt></a> </li>
				51	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				52	in a <tt>Function</tt></a> </li>
				53	<li><a href="#iterate_convert">Turning an iterator into a
				54	class pointer</a> </li>
				55	<li><a href="#iterate_complex">Finding call sites: a more
				56	complex example</a> </li>
				57	<li><a href="#calls_and_invokes">Treating calls and invokes
				58	the same way</a> </li>
				59	<li><a href="#iterate_chains">Iterating over def-use &
				60	use-def chains</a> </li>
				61	</ul>
				62	</li>
				63	<li><a href="#simplechanges">Making simple changes</a>
				64	<ul>
				65	<li><a href="#schanges_creating">Creating and inserting new
				66	<tt>Instruction</tt>s</a> </li>
				67	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				68	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				69	with another <tt>Value</tt></a> </li>
				70	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	71	<!--
				72	<li>Working with the Control Flow Graph
				73	<ul>
				74	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				75	<li>
				76	<li>
				77	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	78	--> </li>
				79	</ul>
				80	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	81	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	82	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	83	<li><a href="#Value">The <tt>Value</tt> class</a>
				84	<ul>
				85	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	86	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	87	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	88	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	89	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt>
				90	class</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	91	</ul></li>
				92	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				93	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	94	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				95	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				96	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class
				97	</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	98	</ul></li>
				99	<li><a href="#Module">The <tt>Module</tt> class</a></li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	100	<li><a href="#Constant">The <tt>Constant</tt> class</a></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	101	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	102	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
				103	</ul></li>
				104	</ul></li>
				105	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				106	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				107	<ul>
				108	<li>Creating, inserting, moving and deleting from LLVM lists </li>
				109	</ul>
				110	</li>
				111	<li>Important iterator invalidation semantics to be aware of.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	112	</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	113	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	114
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	115	<div class="doc_author">
				116	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner	94c4359	2004-05-26 16:52:55 +0000	[diff] [blame]	117	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
				118	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
				119	<a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	120	</div>
				121
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	122	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	123	<div class="doc_section">
				124	<a name="introduction">Introduction </a>
				125	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	126	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	127
				128	<div class="doc_text">
				129
				130	<p>This document is meant to highlight some of the important classes and
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	131	interfaces available in the LLVM source-base. This manual is not
				132	intended to explain what LLVM is, how it works, and what LLVM code looks
				133	like. It assumes that you know the basics of LLVM and are interested
				134	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	135	code.</p>
				136
				137	<p>This document should get you oriented so that you can find your
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	138	way in the continuously growing source code that makes up the LLVM
				139	infrastructure. Note that this manual is not intended to serve as a
				140	replacement for reading the source code, so if you think there should be
				141	a method in one of these classes to do something, but it's not listed,
				142	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				143	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	144
				145	<p>The first section of this document describes general information that is
				146	useful to know when working in the LLVM infrastructure, and the second describes
				147	the Core LLVM classes. In the future this manual will be extended with
				148	information describing how to use extension libraries, such as dominator
				149	information, CFG traversal routines, and useful utilities like the <tt><a
				150	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				151
				152	</div>
				153
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	154	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	155	<div class="doc_section">
				156	<a name="general">General Information</a>
				157	</div>
				158	<!-- *********************************************************************** -->
				159
				160	<div class="doc_text">
				161
				162	<p>This section contains general information that is useful if you are working
				163	in the LLVM source-base, but that isn't specific to any particular API.</p>
				164
				165	</div>
				166
				167	<!-- ======================================================================= -->
				168	<div class="doc_subsection">
				169	<a name="stl">The C++ Standard Template Library</a>
				170	</div>
				171
				172	<div class="doc_text">
				173
				174	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	175	perhaps much more than you are used to, or have seen before. Because of
				176	this, you might want to do a little background reading in the
				177	techniques used and capabilities of the library. There are many good
				178	pages that discuss the STL, and several books on the subject that you
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	179	can get, so it will not be discussed in this document.</p>
				180
				181	<p>Here are some useful links:</p>
				182
				183	<ol>
				184
				185	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				186	reference</a> - an excellent reference for the STL and other parts of the
				187	standard C++ library.</li>
				188
				189	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
				190	O'Reilly book in the making. It has a decent <a
				191	href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
				192	Reference</a> that rivals Dinkumware's, and is actually free until the book is
				193	published.</li>
				194
				195	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				196	Questions</a></li>
				197
				198	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				199	Contains a useful <a
				200	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				201	STL</a>.</li>
				202
				203	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				204	Page</a></li>
				205
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	206	<li><a href="http://www.linux.com.cn/Bruce_Eckel/TICPPv2/Contents.htm">
				207	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				208	the book).</a></li>
				209
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	210	</ol>
				211
				212	<p>You are also encouraged to take a look at the <a
				213	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				214	to write maintainable code more than where to put your curly braces.</p>
				215
				216	</div>
				217
				218	<!-- ======================================================================= -->
				219	<div class="doc_subsection">
				220	<a name="stl">Other useful references</a>
				221	</div>
				222
				223	<div class="doc_text">
				224
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	225	<ol>
				226	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	227	Branch and Tag Primer</a></li>
Misha Brukman	a0f71e4	2004-06-18 18:39:00 +0000	[diff] [blame^]	228	<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
				229	static and shared libraries across platforms</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	230	</ol>
				231
				232	</div>
				233
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	234	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	235	<div class="doc_section">
				236	<a name="apis">Important and useful LLVM APIs</a>
				237	</div>
				238	<!-- *********************************************************************** -->
				239
				240	<div class="doc_text">
				241
				242	<p>Here we highlight some LLVM APIs that are generally useful and good to
				243	know about when writing transformations.</p>
				244
				245	</div>
				246
				247	<!-- ======================================================================= -->
				248	<div class="doc_subsection">
				249	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				250	</div>
				251
				252	<div class="doc_text">
				253
				254	<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	255	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				256	operator, but they don't have some drawbacks (primarily stemming from
				257	the fact that <tt>dynamic_cast<></tt> only works on classes that
				258	have a v-table). Because they are used so often, you must know what they
				259	do and how they work. All of these templates are defined in the <a
				260	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	261	file (note that you very rarely have to include this file directly).</p>
				262
				263	<dl>
				264	<dt><tt>isa<></tt>: </dt>
				265
				266	<dd>The <tt>isa<></tt> operator works exactly like the Java
				267	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				268	a reference or pointer points to an instance of the specified class. This can
				269	be very useful for constraint checking of various sorts (example below).</dd>
				270
				271	<dt><tt>cast<></tt>: </dt>
				272
				273	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				274	converts a pointer or reference from a base class to a derived cast, causing
				275	an assertion failure if it is not really an instance of the right type. This
				276	should be used in cases where you have some information that makes you believe
				277	that something is of the right type. An example of the <tt>isa<></tt>
				278	and <tt>cast<></tt> template is:
				279
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	280	<pre>
				281	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				282	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				283	return true;
				284
				285	<i>// Otherwise, it must be an instruction...</i>
				286	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				287	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	288
				289	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				290	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				291	operator.</p>
				292
				293	</dd>
				294
				295	<dt><tt>dyn_cast<></tt>:</dt>
				296
				297	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				298	checks to see if the operand is of the specified type, and if so, returns a
				299	pointer to it (this operator does not work with references). If the operand is
				300	not of the correct type, a null pointer is returned. Thus, this works very
				301	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				302	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				303	in an <tt>if</tt> statement or some other flow control statement like this:
				304
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	305	<pre>
				306	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				307	...
				308	}
				309	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	310
				311	<p> This form of the <tt>if</tt> statement effectively combines together a
				312	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				313	statement, which is very convenient.</p>
				314
				315	<p> Another common example is:</p>
				316
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	317	<pre>
				318	<i>// Loop over all of the phi nodes in a basic block</i>
				319	BasicBlock::iterator BBI = BB->begin();
				320	for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(BBI); ++BBI)
				321	std::cerr << *PN;
				322	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	323
				324	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				325	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				326	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				327	check for lots of different variants of classes. If you find yourself
				328	wanting to do this, it is much cleaner and more efficient to use the
				329	InstVisitor class to dispatch over the instruction type directly.</p>
				330
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	331	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	332
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	333	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	334
				335	<dd>The <tt>cast_or_null<></tt> operator works just like the
				336	<tt>cast<></tt> operator, except that it allows for a null pointer as
				337	an argument (which it then propagates). This can sometimes be useful,
				338	allowing you to combine several null checks into one.</dd>
				339
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	340	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	341
				342	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				343	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				344	as an argument (which it then propagates). This can sometimes be useful,
				345	allowing you to combine several null checks into one.</dd>
				346
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	347	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	348
				349	<p>These five templates can be used with any classes, whether they have a
				350	v-table or not. To add support for these templates, you simply need to add
				351	<tt>classof</tt> static methods to the class you are interested casting
				352	to. Describing this is currently outside the scope of this document, but there
				353	are lots of examples in the LLVM source base.</p>
				354
				355	</div>
				356
				357	<!-- ======================================================================= -->
				358	<div class="doc_subsection">
				359	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				360	</div>
				361
				362	<div class="doc_text">
				363
				364	<p>Often when working on your pass you will put a bunch of debugging printouts
				365	and other code into your pass. After you get it working, you want to remove
				366	it... but you may need it again in the future (to work out new bugs that you run
				367	across).</p>
				368
				369	<p> Naturally, because of this, you don't want to delete the debug printouts,
				370	but you don't want them to always be noisy. A standard compromise is to comment
				371	them out, allowing you to enable them if you need them in the future.</p>
				372
				373	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				374	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				375	this problem. Basically, you can put arbitrary code into the argument of the
				376	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				377	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				378
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	379	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	380
				381	<p>Then you can run your pass like this:</p>
				382
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	383	<pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> I am here!<br> $<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	384
				385	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				386	to not have to create "yet another" command line option for the debug output for
				387	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				388	so they do not cause a performance impact at all (for the same reason, they
				389	should also not contain side-effects!).</p>
				390
				391	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				392	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				393	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				394	program hasn't been started yet, you can always just run it with
				395	<tt>-debug</tt>.</p>
				396
				397	</div>
				398
				399	<!-- _______________________________________________________________________ -->
				400	<div class="doc_subsubsection">
				401	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				402	the <tt>-debug-only</tt> option</a>
				403	</div>
				404
				405	<div class="doc_text">
				406
				407	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				408	just turns on <b>too much</b> information (such as when working on the code
				409	generator). If you want to enable debug information with more fine-grained
				410	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				411	option as follows:</p>
				412
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	413	<pre> ...<br> DEBUG(std::cerr << "No debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "foo"<br> DEBUG(std::cerr << "'foo' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE "bar"<br> DEBUG(std::cerr << "'bar' debug type\n");<br> #undef DEBUG_TYPE<br> #define DEBUG_TYPE ""<br> DEBUG(std::cerr << "No debug type (2)\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	414
				415	<p>Then you can run your pass like this:</p>
				416
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	417	<pre> $ opt < a.bc > /dev/null -mypass<br> <no output><br> $ opt < a.bc > /dev/null -mypass -debug<br> No debug type<br> 'foo' debug type<br> 'bar' debug type<br> No debug type (2)<br> $ opt < a.bc > /dev/null -mypass -debug-only=foo<br> 'foo' debug type<br> $ opt < a.bc > /dev/null -mypass -debug-only=bar<br> 'bar' debug type<br> $<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	418
				419	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				420	a file, to specify the debug type for the entire module (if you do this before
				421	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				422	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				423	"bar", because there is no system in place to ensure that names do not
				424	conflict. If two different modules use the same string, they will all be turned
				425	on when the name is specified. This allows, for example, all debug information
				426	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	427	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	428
				429	</div>
				430
				431	<!-- ======================================================================= -->
				432	<div class="doc_subsection">
				433	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				434	option</a>
				435	</div>
				436
				437	<div class="doc_text">
				438
				439	<p>The "<tt><a
				440	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				441	provides a template named <tt>Statistic</tt> that is used as a unified way to
				442	keep track of what the LLVM compiler is doing and how effective various
				443	optimizations are. It is useful to see what optimizations are contributing to
				444	making a particular program run faster.</p>
				445
				446	<p>Often you may run your pass on some big program, and you're interested to see
				447	how many times it makes a certain transformation. Although you can do this with
				448	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				449	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				450	keep track of this information, and the calculated information is presented in a
				451	uniform manner with the rest of the passes being executed.</p>
				452
				453	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				454	it are as follows:</p>
				455
				456	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	457	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	458	<pre>static Statistic<> NumXForms("mypassname", "The # of times I did stuff");<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	459
				460	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				461	but if you do not specify a template argument, it defaults to acting like
				462	an unsigned int counter (this is usually what you want).</p></li>
				463
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	464	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	465	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	466	</li>
				467	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	468
				469	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				470	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				471
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	472	<pre> $ opt -stats -mypassname < program.bc > /dev/null<br> ... statistic output ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	473
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	474	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				475	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	476
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	477	<pre> 7646 bytecodewriter - Number of normal instructions<br> 725 bytecodewriter - Number of oversized instructions<br> 129996 bytecodewriter - Number of bytecode bytes written<br> 2817 raise - Number of insts DCEd or constprop'd<br> 3213 raise - Number of cast-of-self removed<br> 5046 raise - Number of expression trees converted<br> 75 raise - Number of other getelementptr's formed<br> 138 raise - Number of load/store peepholes<br> 42 deadtypeelim - Number of unused typenames removed from symtab<br> 392 funcresolve - Number of varargs functions resolved<br> 27 globaldce - Number of global variables removed<br> 2 adce - Number of basic blocks removed<br> 134 cee - Number of branches revectored<br> 49 cee - Number of setcc instruction eliminated<br> 532 gcse - Number of loads removed<br> 2919 gcse - Number of instructions removed<br> 86 indvars - Number of canonical indvars added<br> 87 indvars - Number of aux indvars removed<br> 25 instcombine - Number of dead inst eliminate<br> 434 instcombine - Number of insts combined<br> 248 licm - Number of load insts hoisted<br> 1298 licm - Number of insts hoisted to a loop pre-header<br> 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)<br> 75 mem2reg - Number of alloca's promoted<br> 1444 cfgsimplify - Number of blocks simplified<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	478
				479	<p>Obviously, with so many optimizations, having a unified framework for this
				480	stuff is very nice. Making your pass fit well into the framework makes it more
				481	maintainable and useful.</p>
				482
				483	</div>
				484
				485	<!-- *********************************************************************** -->
				486	<div class="doc_section">
				487	<a name="common">Helpful Hints for Common Operations</a>
				488	</div>
				489	<!-- *********************************************************************** -->
				490
				491	<div class="doc_text">
				492
				493	<p>This section describes how to perform some very simple transformations of
				494	LLVM code. This is meant to give examples of common idioms used, showing the
				495	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				496	you should also read about the main classes that you will be working with. The
				497	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				498	and descriptions of the main classes that you should know about.</p>
				499
				500	</div>
				501
				502	<!-- NOTE: this section should be heavy on example code -->
				503	<!-- ======================================================================= -->
				504	<div class="doc_subsection">
				505	<a name="inspection">Basic Inspection and Traversal Routines</a>
				506	</div>
				507
				508	<div class="doc_text">
				509
				510	<p>The LLVM compiler infrastructure have many different data structures that may
				511	be traversed. Following the example of the C++ standard template library, the
				512	techniques used to traverse these various data structures are all basically the
				513	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				514	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				515	function returns an iterator pointing to one past the last valid element of the
				516	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				517	between the two operations.</p>
				518
				519	<p>Because the pattern for iteration is common across many different aspects of
				520	the program representation, the standard template library algorithms may be used
				521	on them, and it is easier to remember how to iterate. First we show a few common
				522	examples of the data structures that need to be traversed. Other data
				523	structures are traversed in very similar ways.</p>
				524
				525	</div>
				526
				527	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	528	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	529	<a name="iterate_function">Iterating over the </a><a
				530	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				531	href="#Function"><tt>Function</tt></a>
				532	</div>
				533
				534	<div class="doc_text">
				535
				536	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				537	transform in some way; in particular, you'd like to manipulate its
				538	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				539	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				540	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				541	<tt>Instruction</tt>s it contains:</p>
				542
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	543	<pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> cerr << "Basic block (name=" << i->getName() << ") has " <br> << i->size() << " instructions.\n";<br> }<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	544
				545	<p>Note that i can be used as if it were a pointer for the purposes of
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	546	invoking member functions of the <tt>Instruction</tt> class. This is
				547	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	548	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	549	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				550
				551	</div>
				552
				553	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	554	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	555	<a name="iterate_basicblock">Iterating over the </a><a
				556	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				557	href="#BasicBlock"><tt>BasicBlock</tt></a>
				558	</div>
				559
				560	<div class="doc_text">
				561
				562	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				563	easy to iterate over the individual instructions that make up
				564	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				565	a <tt>BasicBlock</tt>:</p>
				566
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	567	<pre> // blk is a pointer to a BasicBlock instance<br> for (BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)<br> // the next statement works since operator<<(ostream&,...) <br> // is overloaded for Instruction&<br> cerr << *i << "\n";<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	568
				569	<p>However, this isn't really the best way to print out the contents of a
				570	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				571	anything you'll care about, you could have just invoked the print routine on the
				572	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				573
				574	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				575	it will print out the contents of the pointer, instead of the pointer value you
				576	might expect. This is a deprecated interface that will be removed in the
				577	future, so it's best not to depend on it. To print out the pointer value for
				578	now, you must cast to <tt>void*</tt>.</p>
				579
				580	</div>
				581
				582	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	583	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	584	<a name="iterate_institer">Iterating over the </a><a
				585	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				586	href="#Function"><tt>Function</tt></a>
				587	</div>
				588
				589	<div class="doc_text">
				590
				591	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				592	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				593	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				594	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				595	and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	596	small example that shows how to dump all instructions in a function to the standard error stream:<p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	597
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	598	<pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> cerr << *i << "\n";<br></pre>
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	599	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				600	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	601	initialize a worklist to contain all instructions in a <tt>Function</tt>
				602	F, all you would need to do is something like:
				603	<pre>std::set<Instruction*> worklist;<br>worklist.insert(inst_begin(F), inst_end(F));<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	604
				605	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				606	<tt>Function</tt> pointed to by F.</p>
				607
				608	</div>
				609
				610	<!-- _______________________________________________________________________ -->
				611	<div class="doc_subsubsection">
				612	<a name="iterate_convert">Turning an iterator into a class pointer (and
				613	vice-versa)</a>
				614	</div>
				615
				616	<div class="doc_text">
				617
				618	<p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	619	instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	620	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	621	Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	622	is a <tt>BasicBlock::const_iterator</tt>:</p>
				623
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	624	<pre> Instruction& inst = i; // grab reference to instruction reference<br> Instruction pinst = &i; // grab pointer to instruction reference<br> const Instruction& inst = j;<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	625
				626	<p>However, the iterators you'll be working with in the LLVM framework are
				627	special: they will automatically convert to a ptr-to-instance type whenever they
				628	need to. Instead of dereferencing the iterator and then taking the address of
				629	the result, you can simply assign the iterator to the proper pointer type and
				630	you get the dereference and address-of operation as a result of the assignment
				631	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				632	the last line of the last example,</p>
				633
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	634	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	635
				636	<p>is semantically equivalent to</p>
				637
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	638	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	639
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	640	<p>It's also possible to turn a class pointer into the corresponding iterator,
				641	and this is a constant time operation (very efficient). The following code
				642	snippet illustrates use of the conversion constructors provided by LLVM
				643	iterators. By using these, you can explicitly grab the iterator of something
				644	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	645
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	646	<pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after inst.<br> if (it != inst->getParent()->end()) cerr << it << "\n";<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	647
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	648	</div>
				649
				650	<!--_______________________________________________________________________-->
				651	<div class="doc_subsubsection">
				652	<a name="iterate_complex">Finding call sites: a slightly more complex
				653	example</a>
				654	</div>
				655
				656	<div class="doc_text">
				657
				658	<p>Say that you're writing a FunctionPass and would like to count all the
				659	locations in the entire module (that is, across every <tt>Function</tt>) where a
				660	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				661	learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	662	much more straight-forward manner, but this example will allow us to explore how
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	663	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				664	is what we want to do:</p>
				665
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	666	<pre>initialize callCounter to zero<br>for each Function f in the Module<br> for each BasicBlock b in f<br> for each Instruction i in b<br> if (i is a CallInst and calls the given function)<br> increment callCounter<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	667
				668	<p>And the actual code is (remember, since we're writing a
				669	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				670	override the <tt>runOnFunction</tt> method...):</p>
				671
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	672	<pre>Function* targetFunc = ...;<br><br>class OurFunctionPass : public FunctionPass {<br> public:<br> OurFunctionPass(): callCounter(0) { }<br><br> virtual runOnFunction(Function& F) {<br> for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {<br> for (BasicBlock::iterator i = b->begin(); ie = b->end(); i != ie; ++i) {<br> if (<a
				673	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				674	href="#CallInst">CallInst</a>>(&*i)) {<br> // we know we've encountered a call instruction, so we<br> // need to determine if it's a call to the<br> // function pointed to by m_func or not.<br> <br> if (callInst->getCalledFunction() == targetFunc)<br> ++callCounter;<br> }<br> }<br> }<br> <br> private:<br> unsigned callCounter;<br>};<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	675
				676	</div>
				677
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	678	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	679	<div class="doc_subsubsection">
				680	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				681	</div>
				682
				683	<div class="doc_text">
				684
				685	<p>You may have noticed that the previous example was a bit oversimplified in
				686	that it did not deal with call sites generated by 'invoke' instructions. In
				687	this, and in other situations, you may find that you want to treat
				688	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				689	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				690	less closely-related things. For these cases, LLVM provides a handy wrapper
				691	class called <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	692	href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	693	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				694	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	695	<tt>InvokeInst</tt>s.</p>
				696
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	697	<p>This class has "value semantics": it should be passed by value, not by
				698	reference and it should not be dynamically allocated or deallocated using
				699	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				700	assignable and constructable, with costs equivalents to that of a bare pointer.
				701	If you look at its definition, it has only a single pointer member.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	702
				703	</div>
				704
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	705	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	706	<div class="doc_subsubsection">
				707	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				708	</div>
				709
				710	<div class="doc_text">
				711
				712	<p>Frequently, we might have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	713	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				714	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				715	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				716	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				717	particular function <tt>foo</tt>. Finding all of the instructions that
				718	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				719	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	720
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	721	<pre>Function* F = ...;<br><br>for (Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {<br> if (Instruction Inst = dyn_cast<Instruction>(i)) {<br> cerr << "F is used in instruction:\n";<br> cerr << *Inst << "\n";<br> }<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	722
				723	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	724	href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	725	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				726	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				727	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				728	all of the values that a particular instruction uses (that is, the operands of
				729	the particular <tt>Instruction</tt>):</p>
				730
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	731	<pre>Instruction* pi = ...;<br><br>for (User::op_iterator i = pi->op_begin(), e = pi->op_end(); i != e; ++i) {<br> Value* v = *i;<br> ...<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	732
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	733	<!--
				734	def-use chains ("finding all users of"): Value::use_begin/use_end
				735	use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	736	-->
				737
				738	</div>
				739
				740	<!-- ======================================================================= -->
				741	<div class="doc_subsection">
				742	<a name="simplechanges">Making simple changes</a>
				743	</div>
				744
				745	<div class="doc_text">
				746
				747	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	748	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	749	transformations, it's fairly common to manipulate the contents of basic
				750	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	751	and gives example code.</p>
				752
				753	</div>
				754
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	755	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	756	<div class="doc_subsubsection">
				757	<a name="schanges_creating">Creating and inserting new
				758	<tt>Instruction</tt>s</a>
				759	</div>
				760
				761	<div class="doc_text">
				762
				763	<p><i>Instantiating Instructions</i></p>
				764
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	765	<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	766	constructor for the kind of instruction to instantiate and provide the necessary
				767	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				768	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				769
				770	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				771
				772	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				773	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				774	subclass is likely to have varying default parameters which change the semantics
				775	of the instruction, so refer to the <a
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	776	href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	777	Instruction</a> that you're interested in instantiating.</p>
				778
				779	<p><i>Naming values</i></p>
				780
				781	<p>It is very useful to name the values of instructions when you're able to, as
				782	this facilitates the debugging of your transformations. If you end up looking
				783	at generated LLVM machine code, you definitely want to have logical names
				784	associated with the results of instructions! By supplying a value for the
				785	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				786	associate a logical name with the result of the instruction's execution at
				787	runtime. For example, say that I'm writing a transformation that dynamically
				788	allocates space for an integer on the stack, and that integer is going to be
				789	used as some kind of index by some other code. To accomplish this, I place an
				790	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				791	<tt>Function</tt>, and I'm intending to use it within the same
				792	<tt>Function</tt>. I might do:</p>
				793
				794	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				795
				796	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				797	execution value, which is a pointer to an integer on the runtime stack.</p>
				798
				799	<p><i>Inserting instructions</i></p>
				800
				801	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				802	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				803
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	804	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	805	<li>Insertion into an explicit instruction list
				806
				807	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				808	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				809	before <tt>*pi</tt>, we do the following: </p>
				810
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	811	<pre> BasicBlock pb = ...;<br> Instruction pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre>
				812
				813	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				814	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				815	classes provide constructors which take a pointer to a
				816	<tt>BasicBlock</tt> to be appended to. For example code that
				817	looked like: </p>
				818
				819	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				820
				821	<p>becomes: </p>
				822
				823	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				824
				825	<p>which is much cleaner, especially if you are creating
				826	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	827
				828	<li>Insertion into an implicit instruction list
				829
				830	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				831	are implicitly associated with an existing instruction list: the instruction
				832	list of the enclosing basic block. Thus, we could have accomplished the same
				833	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				834	</p>
				835
				836	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				837
				838	<p>In fact, this sequence of steps occurs so frequently that the
				839	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				840	constructors which take (as a default parameter) a pointer to an
				841	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				842	precede. That is, <tt>Instruction</tt> constructors are capable of
				843	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				844	provided instruction, immediately before that instruction. Using an
				845	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				846	parameter, the above code becomes:</p>
				847
				848	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				849
				850	<p>which is much cleaner, especially if you're creating a lot of
				851	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				852	</ul>
				853
				854	</div>
				855
				856	<!--_______________________________________________________________________-->
				857	<div class="doc_subsubsection">
				858	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				859	</div>
				860
				861	<div class="doc_text">
				862
				863	<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	864	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	865	you must have a pointer to the instruction that you wish to delete. Second, you
				866	need to obtain the pointer to that instruction's basic block. You use the
				867	pointer to the basic block to get its list of instructions and then use the
				868	erase function to remove your instruction. For example:</p>
				869
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	870	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				871	href="#BasicBlock">BasicBlock</a> *BB = I->getParent();<br> BB->getInstList().erase(I);<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	872
				873	</div>
				874
				875	<!--_______________________________________________________________________-->
				876	<div class="doc_subsubsection">
				877	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				878	<tt>Value</tt></a>
				879	</div>
				880
				881	<div class="doc_text">
				882
				883	<p><i>Replacing individual instructions</i></p>
				884
				885	<p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	886	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	887	and <tt>ReplaceInstWithInst</tt>.</p>
				888
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	889	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	890
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	891	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	892	<li><tt>ReplaceInstWithValue</tt>
				893
				894	<p>This function replaces all uses (within a basic block) of a given
				895	instruction with a value, and then removes the original instruction. The
				896	following example illustrates the replacement of the result of a particular
				897	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				898	pointer to an integer.</p>
				899
				900	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				901
				902	<li><tt>ReplaceInstWithInst</tt>
				903
				904	<p>This function replaces a particular instruction with another
				905	instruction. The following example illustrates the replacement of one
				906	<tt>AllocaInst</tt> with another.</p>
				907
				908	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithInst(instToReplace->getParent()->getInstList(), ii,<br> new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));<br></pre></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	909	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	910
				911	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				912
				913	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				914	<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	915	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				916	and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	917	information.</p>
				918
				919	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				920	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				921	ReplaceInstWithValue, ReplaceInstWithInst -->
				922
				923	</div>
				924
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	925	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	926	<div class="doc_section">
				927	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				928	</div>
				929	<!-- *********************************************************************** -->
				930
				931	<div class="doc_text">
				932
				933	<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	934	being inspected or transformed. The core LLVM classes are defined in
				935	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	936	the <tt>lib/VMCore</tt> directory.</p>
				937
				938	</div>
				939
				940	<!-- ======================================================================= -->
				941	<div class="doc_subsection">
				942	<a name="Value">The <tt>Value</tt> class</a>
				943	</div>
				944
				945	<div>
				946
				947	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				948	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	949	doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	950
				951	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				952	base. It represents a typed value that may be used (among other things) as an
				953	operand to an instruction. There are many different types of <tt>Value</tt>s,
				954	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				955	href="#Argument"><tt>Argument</tt></a>s. Even <a
				956	href="#Instruction"><tt>Instruction</tt></a>s and <a
				957	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				958
				959	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				960	for a program. For example, an incoming argument to a function (represented
				961	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				962	every instruction in the function that references the argument. To keep track
				963	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				964	href="#User"><tt>User</tt></a>s that is using it (the <a
				965	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				966	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				967	def-use information in the program, and is accessible through the <tt>use_</tt>*
				968	methods, shown below.</p>
				969
				970	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				971	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				972	method. In addition, all LLVM values can be named. The "name" of the
				973	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				974
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	975	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	976
				977	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				978	that the name of any value may be missing (an empty string), so names should
				979	<b>ONLY</b> be used for debugging (making the source code easier to read,
				980	debugging printouts), they should not be used to keep track of values or map
				981	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				982	<tt>Value</tt> itself instead.</p>
				983
				984	<p>One important aspect of LLVM is that there is no distinction between an SSA
				985	variable and the operation that produces it. Because of this, any reference to
				986	the value produced by an instruction (or the value available as an incoming
Chris Lattner	d5fc4fc	2004-03-18 14:58:55 +0000	[diff] [blame]	987	argument, for example) is represented as a direct pointer to the instance of
				988	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	989	represents this value. Although this may take some getting used to, it
				990	simplifies the representation and makes it easier to manipulate.</p>
				991
				992	</div>
				993
				994	<!-- _______________________________________________________________________ -->
				995	<div class="doc_subsubsection">
				996	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				997	</div>
				998
				999	<div class="doc_text">
				1000
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1001	<ul>
				1002	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1003	use-list<br>
				1004	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1005	the use-list<br>
				1006	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1007	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1008	<tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1009	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1010	the use-list.<br>
				1011	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1012	use-list.<br>
				1013	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1014	element in the list.
				1015	<p> These methods are the interface to access the def-use
				1016	information in LLVM. As with all other iterators in LLVM, the naming
				1017	conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1018	</li>
				1019	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1020	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1021	</li>
				1022	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1023	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1024	<tt>void setName(const std::string &Name)</tt>
				1025	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1026	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1027	</li>
				1028	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1029
				1030	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1031	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1032	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1033	produces a constant value (for example through constant folding), you can
				1034	replace all uses of the instruction with the constant like this:</p>
				1035
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1036	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1037	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1038
				1039	</div>
				1040
				1041	<!-- ======================================================================= -->
				1042	<div class="doc_subsection">
				1043	<a name="User">The <tt>User</tt> class</a>
				1044	</div>
				1045
				1046	<div class="doc_text">
				1047
				1048	<p>
				1049	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1050	doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1051	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1052
				1053	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1054	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1055	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1056	referring to. The <tt>User</tt> class itself is a subclass of
				1057	<tt>Value</tt>.</p>
				1058
				1059	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1060	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1061	Single Assignment (SSA) form, there can only be one definition referred to,
				1062	allowing this direct connection. This connection provides the use-def
				1063	information in LLVM.</p>
				1064
				1065	</div>
				1066
				1067	<!-- _______________________________________________________________________ -->
				1068	<div class="doc_subsubsection">
				1069	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1070	</div>
				1071
				1072	<div class="doc_text">
				1073
				1074	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1075	an index access interface and through an iterator based interface.</p>
				1076
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1077	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1078	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1079	<tt>unsigned getNumOperands()</tt>
				1080	<p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1081	convenient form for direct access.</p></li>
				1082
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1083	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1084	list<br>
				1085	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1086	Get an iterator to the start of the operand list.<br>
				1087	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1088	operand list.
				1089	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1090	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1091	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1092
				1093	</div>
				1094
				1095	<!-- ======================================================================= -->
				1096	<div class="doc_subsection">
				1097	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1098	</div>
				1099
				1100	<div class="doc_text">
				1101
				1102	<p><tt>#include "</tt><tt><a
				1103	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1104	doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1105	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1106	href="#Value"><tt>Value</tt></a></p>
				1107
				1108	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1109	instructions. It provides only a few methods, but is a very commonly used
				1110	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1111	opcode (instruction type) and the parent <a
				1112	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1113	into. To represent a specific type of instruction, one of many subclasses of
				1114	<tt>Instruction</tt> are used.</p>
				1115
				1116	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1117	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1118	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1119	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1120	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1121	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1122	file contains some meta-data about the various different types of instructions
				1123	in LLVM. It describes the enum values that are used as opcodes (for example
				1124	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1125	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1126	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1127	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1128	this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1129	<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1130
				1131	</div>
				1132
				1133	<!-- _______________________________________________________________________ -->
				1134	<div class="doc_subsubsection">
				1135	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1136	class</a>
				1137	</div>
				1138
				1139	<div class="doc_text">
				1140
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1141	<ul>
				1142	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1143	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1144	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1145	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1146	<p>Returns true if the instruction writes to memory, i.e. it is a
				1147	<tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1148	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1149	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1150	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1151	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1152	in all ways to the original except that the instruction has no parent
				1153	(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1154	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1155	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1156
				1157	</div>
				1158
				1159	<!-- ======================================================================= -->
				1160	<div class="doc_subsection">
				1161	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1162	</div>
				1163
				1164	<div class="doc_text">
				1165
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1166	<p><tt>#include "<a
				1167	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1168	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1169	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1170	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1171
				1172	<p>This class represents a single entry multiple exit section of the code,
				1173	commonly known as a basic block by the compiler community. The
				1174	<tt>BasicBlock</tt> class maintains a list of <a
				1175	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1176	Matching the language definition, the last element of this list of instructions
				1177	is always a terminator instruction (a subclass of the <a
				1178	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1179
				1180	<p>In addition to tracking the list of instructions that make up the block, the
				1181	<tt>BasicBlock</tt> class also keeps track of the <a
				1182	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1183
				1184	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1185	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1186	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1187	<tt>label</tt>.</p>
				1188
				1189	</div>
				1190
				1191	<!-- _______________________________________________________________________ -->
				1192	<div class="doc_subsubsection">
				1193	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1194	class</a>
				1195	</div>
				1196
				1197	<div class="doc_text">
				1198
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1199	<ul>
				1200	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
				1201	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1202	<p>The <tt>BasicBlock</tt> constructor is used to create new basic
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1203	blocks for insertion into a function. The constructor optionally takes
				1204	a name for the new block, and a <a href="#Function"><tt>Function</tt></a>
				1205	to insert it into. If the <tt>Parent</tt> parameter is specified, the
				1206	new <tt>BasicBlock</tt> is automatically inserted at the end of the
				1207	specified <a href="#Function"><tt>Function</tt></a>, if not specified,
				1208	the BasicBlock must be manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1209	</li>
				1210	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list
				1211	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1212	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1213	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,<tt>size()</tt>,<tt>empty()</tt>,<tt>rbegin()</tt>,<tt>rend()
				1214	- </tt>STL style functions for accessing the instruction list.
				1215	<p> These methods and typedefs are forwarding functions that have
				1216	the same semantics as the standard library methods of the same names.
				1217	These methods expose the underlying instruction list of a basic block in
				1218	a way that is easy to manipulate. To get the full complement of
				1219	container operations (including operations to update the list), you must
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1220	use the <tt>getInstList()</tt> method.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1221	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1222	<p> This method is used to get access to the underlying container
				1223	that actually holds the Instructions. This method must be used when
				1224	there isn't a forwarding function in the <tt>BasicBlock</tt> class for
				1225	the operation that you would like to perform. Because there are no
				1226	forwarding functions for "updating" operations, you need to use this if
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1227	you want to update the contents of a <tt>BasicBlock</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1228	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1229	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1230	the block is embedded into, or a null pointer if it is homeless.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1231	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1232	<p> Returns a pointer to the terminator instruction that appears at
				1233	the end of the <tt>BasicBlock</tt>. If there is no terminator
				1234	instruction, or if the last instruction in the block is not a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1235	terminator, then a null pointer is returned.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1236	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1237
				1238	</div>
				1239
				1240	<!-- ======================================================================= -->
				1241	<div class="doc_subsection">
				1242	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1243	</div>
				1244
				1245	<div class="doc_text">
				1246
				1247	<p><tt>#include "<a
				1248	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1249	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1250	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1251	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1252	href="#Value"><tt>Value</tt></a></p>
				1253
				1254	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1255	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1256	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1257	Because they are visible at global scope, they are also subject to linking with
				1258	other globals defined in different translation units. To control the linking
				1259	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1260	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
				1261	defined by the <tt>LinkageTypes</tt> enumerator.</p>
				1262
				1263	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1264	<tt>static</tt> in C), it is not visible to code outside the current translation
				1265	unit, and does not participate in linking. If it has external linkage, it is
				1266	visible to external code, and does participate in linking. In addition to
				1267	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1268	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1269
				1270	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1271	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1272	global is always a pointer to its contents. It is important to remember this
				1273	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1274	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1275	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1276	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1277	the address of the first element of this array and the value of the
				1278	<tt>GlobalVariable</tt> are the same, they have different types. The
				1279	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1280	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1281	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1282	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1283	Language Reference Manual</a>.</p>
				1284
				1285	</div>
				1286
				1287	<!-- _______________________________________________________________________ -->
				1288	<div class="doc_subsubsection">
				1289	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1290	class</a>
				1291	</div>
				1292
				1293	<div class="doc_text">
				1294
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1295	<ul>
				1296	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1297	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1298	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1299	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1300	<p> </p>
				1301	</li>
				1302	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1303	<p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1304	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1305	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1306
				1307	</div>
				1308
				1309	<!-- ======================================================================= -->
				1310	<div class="doc_subsection">
				1311	<a name="Function">The <tt>Function</tt> class</a>
				1312	</div>
				1313
				1314	<div class="doc_text">
				1315
				1316	<p><tt>#include "<a
				1317	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1318	info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
				1319	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1320	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1321
				1322	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1323	actually one of the more complex classes in the LLVM heirarchy because it must
				1324	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1325	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1326	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1327	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1328
				1329	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1330	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1331	ordering of the blocks in the function, which indicate how the code will be
				1332	layed out by the backend. Additionally, the first <a
				1333	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1334	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1335	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1336	nodes from a single <tt>Function</tt>. If the <a
				1337	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1338	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1339	function hasn't been linked in yet.</p>
				1340
				1341	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1342	<tt>Function</tt> class also keeps track of the list of formal <a
				1343	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1344	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1345	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1346	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1347
				1348	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1349	LLVM feature that is only used when you have to look up a value by name. Aside
				1350	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1351	internally to make sure that there are not conflicts between the names of <a
				1352	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1353	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1354	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1355
				1356	</div>
				1357
				1358	<!-- _______________________________________________________________________ -->
				1359	<div class="doc_subsubsection">
				1360	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1361	class</a>
				1362	</div>
				1363
				1364	<div class="doc_text">
				1365
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1366	<ul>
				1367	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1368	Ty, bool isInternal, const std::string &N = "", Module Parent = 0)</tt>
				1369
				1370	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1371	the the program. The constructor must specify the type of the function to
				1372	create and whether or not it should start out with internal or external
				1373	linkage. The <a href="#FunctionType"><tt>FunctionType</tt></a> argument
				1374	specifies the formal arguments and return value for the function. The same
				1375	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1376	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1377	in which the function is defined. If this argument is provided, the function
				1378	will automatically be inserted into that module's list of
				1379	functions.</p></li>
				1380
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1381	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1382
				1383	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1384	function is "external", it does not have a body, and thus must be resolved
				1385	by linking with a function defined in a different translation unit.</p></li>
				1386
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1387	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1388	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1389
				1390	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1391	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1392
				1393	<p>These are forwarding methods that make it easy to access the contents of
				1394	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1395	list.</p></li>
				1396
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1397	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1398
				1399	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1400	is necessary to use when you need to update the list or perform a complex
				1401	action that doesn't have a forwarding method.</p></li>
				1402
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1403	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1404	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1405	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1406
				1407	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1408	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1409
				1410	<p>These are forwarding methods that make it easy to access the contents of
				1411	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1412	list.</p></li>
				1413
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1414	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1415
				1416	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1417	necessary to use when you need to update the list or perform a complex
				1418	action that doesn't have a forwarding method.</p></li>
				1419
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1420	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1421
				1422	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1423	function. Because the entry block for the function is always the first
				1424	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1425
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1426	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1427	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1428
				1429	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1430	<tt>Function</tt> and returns the return type of the function, or the <a
				1431	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1432	function.</p></li>
				1433
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1434	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1435
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1436	<p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1437	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1438	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1439
				1440	</div>
				1441
				1442	<!-- ======================================================================= -->
				1443	<div class="doc_subsection">
				1444	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1445	</div>
				1446
				1447	<div class="doc_text">
				1448
				1449	<p><tt>#include "<a
				1450	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1451	<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1452	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1453	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1454	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1455
				1456	<p>Global variables are represented with the (suprise suprise)
				1457	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1458	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1459	always referenced by their address (global values must live in memory, so their
				1460	"name" refers to their address). See <a
				1461	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1462	may have an initial value (which must be a <a
				1463	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1464	may be marked as "constant" themselves (indicating that their contents never
				1465	change at runtime).</p>
				1466
				1467	</div>
				1468
				1469	<!-- _______________________________________________________________________ -->
				1470	<div class="doc_subsubsection">
				1471	<a name="m_GlobalVariable">Important Public Members of the
				1472	<tt>GlobalVariable</tt> class</a>
				1473	</div>
				1474
				1475	<div class="doc_text">
				1476
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1477	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1478	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1479	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1480	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1481
				1482	<p>Create a new global variable of the specified type. If
				1483	<tt>isConstant</tt> is true then the global variable will be marked as
				1484	unchanging for the program. The Linkage parameter specifies the type of
				1485	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1486	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1487	the resultant global variable will have internal linkage. AppendingLinkage
				1488	concatenates together all instances (in different translation units) of the
				1489	variable into a single variable but is only applicable to arrays.  See
				1490	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1491	further details on linkage types. Optionally an initializer, a name, and the
				1492	module to put the variable into may be specified for the global variable as
				1493	well.</p></li>
				1494
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1495	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1496
				1497	<p>Returns true if this is a global variable that is known not to
				1498	be modified at runtime.</p></li>
				1499
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1500	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1501
				1502	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1503
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1504	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1505
				1506	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1507	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1508	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1509
				1510	</div>
				1511
				1512	<!-- ======================================================================= -->
				1513	<div class="doc_subsection">
				1514	<a name="Module">The <tt>Module</tt> class</a>
				1515	</div>
				1516
				1517	<div class="doc_text">
				1518
				1519	<p><tt>#include "<a
				1520	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1521	<a href="/doxygen/structllvm_1_1Module.html">Module Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1522
				1523	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1524	programs. An LLVM module is effectively either a translation unit of the
				1525	original program or a combination of several translation units merged by the
				1526	linker. The <tt>Module</tt> class keeps track of a list of <a
				1527	href="#Function"><tt>Function</tt></a>s, a list of <a
				1528	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1529	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1530	helpful member functions that try to make common operations easy.</p>
				1531
				1532	</div>
				1533
				1534	<!-- _______________________________________________________________________ -->
				1535	<div class="doc_subsubsection">
				1536	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1537	</div>
				1538
				1539	<div class="doc_text">
				1540
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1541	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1542	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1543	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1544
				1545	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1546	provide a name for it (probably based on the name of the translation unit).</p>
				1547
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1548	<ul>
				1549	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1550	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1551
				1552	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1553	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1554
				1555	<p>These are forwarding methods that make it easy to access the contents of
				1556	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1557	list.</p></li>
				1558
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1559	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1560
				1561	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1562	necessary to use when you need to update the list or perform a complex
				1563	action that doesn't have a forwarding method.</p>
				1564
				1565	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1566	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1567
				1568	<hr>
				1569
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1570	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1571	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1572
				1573	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1574
				1575	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1576	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1577
				1578	<p> These are forwarding methods that make it easy to access the contents of
				1579	a <tt>Module</tt> object's <a
				1580	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1581
				1582	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1583
				1584	<p>Returns the list of <a
				1585	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1586	use when you need to update the list or perform a complex action that
				1587	doesn't have a forwarding method.</p>
				1588
				1589	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1590	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1591
				1592	<hr>
				1593
				1594	<ul>
				1595	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1596
				1597	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1598	for this <tt>Module</tt>.</p>
				1599
				1600	<p><!-- Convenience methods --></p></li>
				1601	</ul>
				1602
				1603	<hr>
				1604
				1605	<ul>
				1606	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1607	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1608
				1609	<p>Look up the specified function in the <tt>Module</tt> <a
				1610	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1611	<tt>null</tt>.</p></li>
				1612
				1613	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1614	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1615
				1616	<p>Look up the specified function in the <tt>Module</tt> <a
				1617	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1618	external declaration for the function and return it.</p></li>
				1619
				1620	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1621
				1622	<p>If there is at least one entry in the <a
				1623	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1624	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1625	string.</p></li>
				1626
				1627	<li><tt>bool addTypeName(const std::string &Name, const <a
				1628	href="#Type">Type</a> *Ty)</tt>
				1629
				1630	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1631	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1632	name, true is returned and the <a
				1633	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1634	</ul>
				1635
				1636	</div>
				1637
				1638	<!-- ======================================================================= -->
				1639	<div class="doc_subsection">
				1640	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1641	</div>
				1642
				1643	<div class="doc_text">
				1644
				1645	<p>Constant represents a base class for different types of constants. It
				1646	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1647	ConstantArray etc for representing the various types of Constants.</p>
				1648
				1649	</div>
				1650
				1651	<!-- _______________________________________________________________________ -->
				1652	<div class="doc_subsubsection">
				1653	<a name="m_Value">Important Public Methods</a>
				1654	</div>
				1655
				1656	<div class="doc_text">
				1657
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1658	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1659	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a
				1660	ConstantExpr
				1661	<hr> Important Subclasses of Constant
				1662	<p> </p>
				1663	<ul>
				1664	<li>ConstantSInt : This subclass of Constant represents a signed
				1665	integer constant.
				1666	<ul>
				1667	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1668	this constant. </li>
				1669	</ul>
				1670	</li>
				1671	<li>ConstantUInt : This class represents an unsigned integer.
				1672	<ul>
				1673	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value
				1674	of this constant. </li>
				1675	</ul>
				1676	</li>
				1677	<li>ConstantFP : This class represents a floating point constant.
				1678	<ul>
				1679	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1680	this constant. </li>
				1681	</ul>
				1682	</li>
				1683	<li>ConstantBool : This represents a boolean constant.
				1684	<ul>
				1685	<li><tt>bool getValue() const</tt>: Returns the underlying value of
				1686	this constant. </li>
				1687	</ul>
				1688	</li>
				1689	<li>ConstantArray : This represents a constant array.
				1690	<ul>
				1691	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1692	Returns a Vecotr of component constants that makeup this array. </li>
				1693	</ul>
				1694	</li>
				1695	<li>ConstantStruct : This represents a constant struct.
				1696	<ul>
				1697	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1698	Returns a Vecotr of component constants that makeup this array. </li>
				1699	</ul>
				1700	</li>
				1701	<li>ConstantPointerRef : This represents a constant pointer value
				1702	that is initialized to point to a global value, which lies at a
				1703	constant fixed address.
				1704	<ul>
				1705	<li><tt>GlobalValue *getValue()</tt>: Returns the global
				1706	value to which this pointer is pointing to. </li>
				1707	</ul>
				1708	</li>
				1709	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1710	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1711	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1712
				1713	</div>
				1714
				1715	<!-- ======================================================================= -->
				1716	<div class="doc_subsection">
				1717	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1718	</div>
				1719
				1720	<div class="doc_text">
				1721
				1722	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1723	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1724	types are instances of subclasses of type like FunctionType, ArrayType
				1725	etc. DerivedType is the interface for all such dervied types including
				1726	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1727	be recursive (StructType). There exists exactly one instance of any type
				1728	structure at a time. This allows using pointer equality of Type *s for comparing
				1729	types.</p>
				1730
				1731	</div>
				1732
				1733	<!-- _______________________________________________________________________ -->
				1734	<div class="doc_subsubsection">
				1735	<a name="m_Value">Important Public Methods</a>
				1736	</div>
				1737
				1738	<div class="doc_text">
				1739
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1740	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1741
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1742	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1743	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1744	not true for Float and Double. </li>
				1745
				1746	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1747	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1748	return false as they do with isSigned. This returns true for UByteTy,
				1749	UShortTy, UIntTy, and ULongTy. </li>
				1750
				1751	<li><tt>bool isInteger() const</tt>: Equilivent to isSigned() \|\| isUnsigned(),
				1752	but with only a single virtual function invocation.</li>
				1753
				1754	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1755	type, which is either Bool type or one of the Integer types.</li>
				1756
				1757	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1758	floating point types.</li>
				1759
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1760	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1761	this type can be converted to 'Ty' without any reinterpretation of bits. For
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1762	example, uint to int or one pointer type to another.</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1763
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1764	<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1765	<p>Derived Types</p>
				1766
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1767	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1768	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1769	<ul>
				1770	<li><tt>const Type * getElementType() const</tt>: Returns the type of
				1771	each of the elements in the sequential type. </li>
				1772	</ul>
				1773	</li>
				1774	<li>ArrayType : This is a subclass of SequentialType and defines
				1775	interface for array types.
				1776	<ul>
				1777	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1778	elements in the array. </li>
				1779	</ul>
				1780	</li>
				1781	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1782	<li>StructType : subclass of DerivedTypes for struct types </li>
				1783	<li>FunctionType : subclass of DerivedTypes for function types.
				1784	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1785	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1786	function</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1787	<li><tt> const Type * getReturnType() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1788	return type of the function.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1789	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1790	the type of the ith parameter.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1791	<li><tt> const unsigned getNumParams() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1792	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1793	</ul>
				1794	</li>
				1795	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1796	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1797	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1798
				1799	</div>
				1800
				1801	<!-- ======================================================================= -->
				1802	<div class="doc_subsection">
				1803	<a name="Argument">The <tt>Argument</tt> class</a>
				1804	</div>
				1805
				1806	<div class="doc_text">
				1807
				1808	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1809	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1810	arguments. An argument has a pointer to the parent Function.</p>
				1811
				1812	</div>
				1813
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1814	<!-- ======================================================================= -->
				1815	<div class="doc_subsection">
				1816	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1817	</div>
				1818	<div class="doc_text">
				1819	<p>This class provides a symbol table that the
				1820	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1821	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1822	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1823	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1824	type. It hides the data it contains and provides access to it through a
				1825	controlled interface.</p>
				1826
				1827	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1828	structure of the information it holds. The class contains two
				1829	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1830	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1831	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1832	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1833	however, are stored in a single dimension and accessed only by name.</p>
				1834
				1835	<p>The interface of this class provides three basic types of operations:
				1836	<ol>
				1837	<li><em>Accessors</em>. Accessors provide read-only access to information
				1838	such as finding a value for a name with the
				1839	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1840	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1841	<tt>SymbolTable</tt> with methods like
				1842	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1843	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1844	of the symbol table in well defined ways, such as the method
				1845	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1846	</ol>
				1847
				1848	<h3>Accessors</h3>
				1849	<dl>
				1850	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1851	</dt>
				1852	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1853	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1854	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1855
				1856	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1857	<dd>The <tt>lookupType</tt> method searches through the types for a
				1858	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1859	is not found, null is returned.</dd>
				1860
				1861	<dt><tt>bool hasTypes() const</tt>:</dt>
				1862	<dd>This function returns true if an entry has been made into the type
				1863	map.</dd>
				1864
				1865	<dt><tt>bool isEmpty() const</tt>:</dt>
				1866	<dd>This function returns true if both the value and types maps are
				1867	empty</dd>
				1868
				1869	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1870	<dd>This function returns the name of the Value provided or the empty
				1871	string if the Value is not in the symbol table.</dd>
				1872
				1873	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1874	<dd>This function returns the name of the Type provided or the empty
				1875	string if the Type is not in the symbol table.</dd>
				1876	</dl>
				1877
				1878	<h3>Mutators</h3>
				1879	<dl>
				1880	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1881	<dd>This method adds the provided value to the symbol table. The Value must
				1882	have both a name and a type which are extracted and used to place the value
				1883	in the correct type plane under the value's name.</dd>
				1884
				1885	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1886	<dd> Inserts a constant or type into the symbol table with the specified
				1887	name. There can be a many to one mapping between names and constants
				1888	or types.</dd>
				1889
				1890	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1891	<dd> Inserts a type into the symbol table with the specified name. There
				1892	can be a many-to-one mapping between names and types. This method
				1893	allows a type with an existing entry in the symbol table to get
				1894	a new name.</dd>
				1895
				1896	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1897	<dd> This method removes a named value from the symbol table. The
				1898	type and name of the Value are extracted from \p N and used to
				1899	lookup the Value in the correct type plane. If the Value is
				1900	not in the symbol table, this method silently ignores the
				1901	request.</dd>
				1902
				1903	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1904	<dd> This method removes a named type from the symbol table. The
				1905	name of the type is extracted from \P T and used to look up
				1906	the Type in the type map. If the Type is not in the symbol
				1907	table, this method silently ignores the request.</dd>
				1908
				1909	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1910	<dd> Remove a constant or type with the specified name from the
				1911	symbol table.</dd>
				1912
				1913	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1914	<dd> Remove a type with the specified name from the symbol table.
				1915	Returns the removed Type.</dd>
				1916
				1917	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1918	<dd> Removes a specific value from the symbol table.
				1919	Returns the removed value.</dd>
				1920
				1921	<dt><tt>bool strip()</tt>:</dt>
				1922	<dd> This method will strip the symbol table of its names leaving
				1923	the type and values. </dd>
				1924
				1925	<dt><tt>void clear()</tt>:</dt>
				1926	<dd>Empty the symbol table completely.</dd>
				1927	</dl>
				1928
				1929	<h3>Iteration</h3>
				1930	<p>The following functions describe three types of iterators you can obtain
				1931	the beginning or end of the sequence for both const and non-const. It is
				1932	important to keep track of the different kinds of iterators. There are
				1933	three idioms worth pointing out:</p>
				1934	<table class="doc_table">
				1935	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1936	<tr>
				1937	<td>Planes Of name/Value maps</td><td>PI</td>
				1938	<td><tt><pre>
				1939	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
				1940	PE = ST.plane_end(); PI != PE; ++PI ) {
				1941	PI->first // This is the Type* of the plane
				1942	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1943	</pre></tt></td>
				1944	</tr>
				1945	<tr>
				1946	<td>All name/Type Pairs</td><td>TI</td>
				1947	<td><tt><pre>
				1948	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1949	TE = ST.type_end(); TI != TE; ++TI )
				1950	TI->first // This is the name of the type
				1951	TI->second // This is the Type* value associated with the name
				1952	</pre></tt></td>
				1953	</tr>
				1954	<tr>
				1955	<td>name/Value pairs in a plane</td><td>VI</td>
				1956	<td><tt><pre>
				1957	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1958	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1959	VI->first // This is the name of the Value
				1960	VI->second // This is the Value* value associated with the name
				1961	</pre></tt></td>
				1962	</tr>
				1963	</table>
				1964	<p>Using the recommended iterator names and idioms will help you avoid
				1965	making mistakes. Of particular note, make sure that whenever you use
				1966	value_begin(SomeType) that you always compare the resulting iterator
				1967	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1968	will loop infinitely.</p>
				1969
				1970	<dl>
				1971
				1972	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1973	<dd>Get an iterator that starts at the beginning of the type planes.
				1974	The iterator will iterate over the Type/ValueMap pairs in the
				1975	type planes. </dd>
				1976
				1977	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1978	<dd>Get a const_iterator that starts at the beginning of the type
				1979	planes. The iterator will iterate over the Type/ValueMap pairs
				1980	in the type planes. </dd>
				1981
				1982	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1983	<dd>Get an iterator at the end of the type planes. This serves as
				1984	the marker for end of iteration over the type planes.</dd>
				1985
				1986	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				1987	<dd>Get a const_iterator at the end of the type planes. This serves as
				1988	the marker for end of iteration over the type planes.</dd>
				1989
				1990	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1991	<dd>Get an iterator that starts at the beginning of a type plane.
				1992	The iterator will iterate over the name/value pairs in the type plane.
				1993	Note: The type plane must already exist before using this.</dd>
				1994
				1995	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				1996	<dd>Get a const_iterator that starts at the beginning of a type plane.
				1997	The iterator will iterate over the name/value pairs in the type plane.
				1998	Note: The type plane must already exist before using this.</dd>
				1999
				2000	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				2001	<dd>Get an iterator to the end of a type plane. This serves as the marker
				2002	for end of iteration of the type plane.
				2003	Note: The type plane must already exist before using this.</dd>
				2004
				2005	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				2006	<dd>Get a const_iterator to the end of a type plane. This serves as the
				2007	marker for end of iteration of the type plane.
				2008	Note: the type plane must already exist before using this.</dd>
				2009
				2010	<dt><tt>type_iterator type_begin()</tt>:</dt>
				2011	<dd>Get an iterator to the start of the name/Type map.</dd>
				2012
				2013	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				2014	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				2015
				2016	<dt><tt>type_iterator type_end()</tt>:</dt>
				2017	<dd>Get an iterator to the end of the name/Type map. This serves as the
				2018	marker for end of iteration of the types.</dd>
				2019
				2020	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2021	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2022	as the marker for end of iteration of the types.</dd>
				2023
				2024	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2025	<dd>This method returns a plane_const_iterator for iteration over
				2026	the type planes starting at a specific plane, given by \p Ty.</dd>
				2027
				2028	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2029	<dd>This method returns a plane_iterator for iteration over the
				2030	type planes starting at a specific plane, given by \p Ty.</dd>
				2031
				2032	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2033	<dd>This method returns a ValueMap* for a specific type plane. This
				2034	interface is deprecated and may go away in the future.</dd>
				2035	</dl>
				2036	</div>
				2037
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2038	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2039	<hr>
				2040	<address>
				2041	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2042	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2043	<a href="http://validator.w3.org/check/referer"><img
				2044	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2045
				2046	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2047	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2048	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2049	Last modified: $Date$
				2050	</address>
				2051
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2052	</body>
				2053	</html>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	2054	<!-- vim: sw=2 noai
				2055	-->