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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>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	18	<li><a href="#stl">The C++ Standard Template Library</a></li>
				19	<!--
				20	<li>The <tt>-time-passes</tt> option</li>
				21	<li>How to use the LLVM Makefile system</li>
				22	<li>How to write a regression test</li>
				23	-->
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	24	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	25	</li>
				26	<li><a href="#apis">Important and useful LLVM APIs</a>
				27	<ul>
				28	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				29	and <tt>dyn_cast<></tt> templates</a> </li>
				30	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				31	option</a>
				32	<ul>
				33	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				34	and the <tt>-debug-only</tt> option</a> </li>
				35	</ul>
				36	</li>
				37	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	38	option</a></li>
				39	<!--
				40	<li>The <tt>InstVisitor</tt> template
				41	<li>The general graph API
				42	-->
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	43	</ul>
				44	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	45	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	46	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	47	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				48	<ul>
				49	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				50	in a <tt>Function</tt></a> </li>
				51	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				52	in a <tt>BasicBlock</tt></a> </li>
				53	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				54	in a <tt>Function</tt></a> </li>
				55	<li><a href="#iterate_convert">Turning an iterator into a
				56	class pointer</a> </li>
				57	<li><a href="#iterate_complex">Finding call sites: a more
				58	complex example</a> </li>
				59	<li><a href="#calls_and_invokes">Treating calls and invokes
				60	the same way</a> </li>
				61	<li><a href="#iterate_chains">Iterating over def-use &
				62	use-def chains</a> </li>
				63	</ul>
				64	</li>
				65	<li><a href="#simplechanges">Making simple changes</a>
				66	<ul>
				67	<li><a href="#schanges_creating">Creating and inserting new
				68	<tt>Instruction</tt>s</a> </li>
				69	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				70	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				71	with another <tt>Value</tt></a> </li>
				72	</ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	73	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	74	<!--
				75	<li>Working with the Control Flow Graph
				76	<ul>
				77	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				78	<li>
				79	<li>
				80	</ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	81	-->
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	82	</ul>
				83	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	84	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	85	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	86	<li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	87	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	88	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	89	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	90	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
				91	<ul>
				92	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
				93	</ul>
				94	</li>
				95	<li><a href="#Module">The <tt>Module</tt> class</a></li>
				96	<li><a href="#Constant">The <tt>Constant</tt> class</a>
				97	<ul>
				98	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				99	<ul>
				100	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				101	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				102	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
				103	</ul>
				104	</li>
				105	</ul>
				106	</li>
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	107	</ul>
				108	</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	109	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	110	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	111	</ul>
				112	</li>
				113	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	114	</li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	115	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				116	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				117	<ul>
				118	<li>Creating, inserting, moving and deleting from LLVM lists </li>
				119	</ul>
				120	</li>
				121	<li>Important iterator invalidation semantics to be aware of.</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	122	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	123
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	124	<div class="doc_author">
				125	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner	94c4359	2004-05-26 16:52:55 +0000	[diff] [blame]	126	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
				127	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
				128	<a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	129	</div>
				130
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	131	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	132	<div class="doc_section">
				133	<a name="introduction">Introduction </a>
				134	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	135	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	136
				137	<div class="doc_text">
				138
				139	<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]	140	interfaces available in the LLVM source-base. This manual is not
				141	intended to explain what LLVM is, how it works, and what LLVM code looks
				142	like. It assumes that you know the basics of LLVM and are interested
				143	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	144	code.</p>
				145
				146	<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]	147	way in the continuously growing source code that makes up the LLVM
				148	infrastructure. Note that this manual is not intended to serve as a
				149	replacement for reading the source code, so if you think there should be
				150	a method in one of these classes to do something, but it's not listed,
				151	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				152	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	153
				154	<p>The first section of this document describes general information that is
				155	useful to know when working in the LLVM infrastructure, and the second describes
				156	the Core LLVM classes. In the future this manual will be extended with
				157	information describing how to use extension libraries, such as dominator
				158	information, CFG traversal routines, and useful utilities like the <tt><a
				159	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				160
				161	</div>
				162
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	163	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	164	<div class="doc_section">
				165	<a name="general">General Information</a>
				166	</div>
				167	<!-- *********************************************************************** -->
				168
				169	<div class="doc_text">
				170
				171	<p>This section contains general information that is useful if you are working
				172	in the LLVM source-base, but that isn't specific to any particular API.</p>
				173
				174	</div>
				175
				176	<!-- ======================================================================= -->
				177	<div class="doc_subsection">
				178	<a name="stl">The C++ Standard Template Library</a>
				179	</div>
				180
				181	<div class="doc_text">
				182
				183	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	184	perhaps much more than you are used to, or have seen before. Because of
				185	this, you might want to do a little background reading in the
				186	techniques used and capabilities of the library. There are many good
				187	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]	188	can get, so it will not be discussed in this document.</p>
				189
				190	<p>Here are some useful links:</p>
				191
				192	<ol>
				193
				194	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				195	reference</a> - an excellent reference for the STL and other parts of the
				196	standard C++ library.</li>
				197
				198	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Tanya Lattner	09cf73c	2004-06-22 04:24:55 +0000	[diff] [blame]	199	O'Reilly book in the making. It has a decent
				200	Standard Library
				201	Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	202	published.</li>
				203
				204	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				205	Questions</a></li>
				206
				207	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				208	Contains a useful <a
				209	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				210	STL</a>.</li>
				211
				212	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				213	Page</a></li>
				214
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	215	<li><a href="http://www.linux.com.cn/Bruce_Eckel/TICPPv2/Contents.htm">
				216	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				217	the book).</a></li>
				218
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	219	</ol>
				220
				221	<p>You are also encouraged to take a look at the <a
				222	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				223	to write maintainable code more than where to put your curly braces.</p>
				224
				225	</div>
				226
				227	<!-- ======================================================================= -->
				228	<div class="doc_subsection">
				229	<a name="stl">Other useful references</a>
				230	</div>
				231
				232	<div class="doc_text">
				233
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	234	<ol>
				235	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	236	Branch and Tag Primer</a></li>
Misha Brukman	a0f71e4	2004-06-18 18:39:00 +0000	[diff] [blame]	237	<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
				238	static and shared libraries across platforms</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	239	</ol>
				240
				241	</div>
				242
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	243	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	244	<div class="doc_section">
				245	<a name="apis">Important and useful LLVM APIs</a>
				246	</div>
				247	<!-- *********************************************************************** -->
				248
				249	<div class="doc_text">
				250
				251	<p>Here we highlight some LLVM APIs that are generally useful and good to
				252	know about when writing transformations.</p>
				253
				254	</div>
				255
				256	<!-- ======================================================================= -->
				257	<div class="doc_subsection">
				258	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				259	</div>
				260
				261	<div class="doc_text">
				262
				263	<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]	264	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				265	operator, but they don't have some drawbacks (primarily stemming from
				266	the fact that <tt>dynamic_cast<></tt> only works on classes that
				267	have a v-table). Because they are used so often, you must know what they
				268	do and how they work. All of these templates are defined in the <a
				269	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	270	file (note that you very rarely have to include this file directly).</p>
				271
				272	<dl>
				273	<dt><tt>isa<></tt>: </dt>
				274
				275	<dd>The <tt>isa<></tt> operator works exactly like the Java
				276	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				277	a reference or pointer points to an instance of the specified class. This can
				278	be very useful for constraint checking of various sorts (example below).</dd>
				279
				280	<dt><tt>cast<></tt>: </dt>
				281
				282	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				283	converts a pointer or reference from a base class to a derived cast, causing
				284	an assertion failure if it is not really an instance of the right type. This
				285	should be used in cases where you have some information that makes you believe
				286	that something is of the right type. An example of the <tt>isa<></tt>
				287	and <tt>cast<></tt> template is:
				288
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	289	<pre>
				290	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				291	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				292	return true;
				293
				294	<i>// Otherwise, it must be an instruction...</i>
				295	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				296	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	297
				298	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				299	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				300	operator.</p>
				301
				302	</dd>
				303
				304	<dt><tt>dyn_cast<></tt>:</dt>
				305
				306	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				307	checks to see if the operand is of the specified type, and if so, returns a
				308	pointer to it (this operator does not work with references). If the operand is
				309	not of the correct type, a null pointer is returned. Thus, this works very
				310	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				311	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				312	in an <tt>if</tt> statement or some other flow control statement like this:
				313
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	314	<pre>
				315	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				316	...
				317	}
				318	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	319
				320	<p> This form of the <tt>if</tt> statement effectively combines together a
				321	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				322	statement, which is very convenient.</p>
				323
				324	<p> Another common example is:</p>
				325
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	326	<pre>
				327	<i>// Loop over all of the phi nodes in a basic block</i>
				328	BasicBlock::iterator BBI = BB->begin();
				329	for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(BBI); ++BBI)
				330	std::cerr << *PN;
				331	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	332
				333	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				334	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				335	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				336	check for lots of different variants of classes. If you find yourself
				337	wanting to do this, it is much cleaner and more efficient to use the
				338	InstVisitor class to dispatch over the instruction type directly.</p>
				339
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	340	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	341
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	342	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	343
				344	<dd>The <tt>cast_or_null<></tt> operator works just like the
				345	<tt>cast<></tt> operator, except that it allows for a null pointer as
				346	an argument (which it then propagates). This can sometimes be useful,
				347	allowing you to combine several null checks into one.</dd>
				348
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	349	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	350
				351	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				352	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				353	as an argument (which it then propagates). This can sometimes be useful,
				354	allowing you to combine several null checks into one.</dd>
				355
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	356	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	357
				358	<p>These five templates can be used with any classes, whether they have a
				359	v-table or not. To add support for these templates, you simply need to add
				360	<tt>classof</tt> static methods to the class you are interested casting
				361	to. Describing this is currently outside the scope of this document, but there
				362	are lots of examples in the LLVM source base.</p>
				363
				364	</div>
				365
				366	<!-- ======================================================================= -->
				367	<div class="doc_subsection">
				368	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				369	</div>
				370
				371	<div class="doc_text">
				372
				373	<p>Often when working on your pass you will put a bunch of debugging printouts
				374	and other code into your pass. After you get it working, you want to remove
				375	it... but you may need it again in the future (to work out new bugs that you run
				376	across).</p>
				377
				378	<p> Naturally, because of this, you don't want to delete the debug printouts,
				379	but you don't want them to always be noisy. A standard compromise is to comment
				380	them out, allowing you to enable them if you need them in the future.</p>
				381
				382	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				383	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				384	this problem. Basically, you can put arbitrary code into the argument of the
				385	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				386	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				387
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	388	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	389
				390	<p>Then you can run your pass like this:</p>
				391
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	392	<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]	393
				394	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				395	to not have to create "yet another" command line option for the debug output for
				396	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				397	so they do not cause a performance impact at all (for the same reason, they
				398	should also not contain side-effects!).</p>
				399
				400	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				401	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				402	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				403	program hasn't been started yet, you can always just run it with
				404	<tt>-debug</tt>.</p>
				405
				406	</div>
				407
				408	<!-- _______________________________________________________________________ -->
				409	<div class="doc_subsubsection">
				410	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				411	the <tt>-debug-only</tt> option</a>
				412	</div>
				413
				414	<div class="doc_text">
				415
				416	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				417	just turns on <b>too much</b> information (such as when working on the code
				418	generator). If you want to enable debug information with more fine-grained
				419	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				420	option as follows:</p>
				421
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	422	<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]	423
				424	<p>Then you can run your pass like this:</p>
				425
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	426	<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]	427
				428	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				429	a file, to specify the debug type for the entire module (if you do this before
				430	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				431	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				432	"bar", because there is no system in place to ensure that names do not
				433	conflict. If two different modules use the same string, they will all be turned
				434	on when the name is specified. This allows, for example, all debug information
				435	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	436	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	437
				438	</div>
				439
				440	<!-- ======================================================================= -->
				441	<div class="doc_subsection">
				442	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				443	option</a>
				444	</div>
				445
				446	<div class="doc_text">
				447
				448	<p>The "<tt><a
				449	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				450	provides a template named <tt>Statistic</tt> that is used as a unified way to
				451	keep track of what the LLVM compiler is doing and how effective various
				452	optimizations are. It is useful to see what optimizations are contributing to
				453	making a particular program run faster.</p>
				454
				455	<p>Often you may run your pass on some big program, and you're interested to see
				456	how many times it makes a certain transformation. Although you can do this with
				457	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				458	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				459	keep track of this information, and the calculated information is presented in a
				460	uniform manner with the rest of the passes being executed.</p>
				461
				462	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				463	it are as follows:</p>
				464
				465	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	466	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	467	<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]	468
				469	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				470	but if you do not specify a template argument, it defaults to acting like
				471	an unsigned int counter (this is usually what you want).</p></li>
				472
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	473	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	474	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	475	</li>
				476	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	477
				478	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				479	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				480
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	481	<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]	482
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	483	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				484	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	485
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	486	<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]	487
				488	<p>Obviously, with so many optimizations, having a unified framework for this
				489	stuff is very nice. Making your pass fit well into the framework makes it more
				490	maintainable and useful.</p>
				491
				492	</div>
				493
				494	<!-- *********************************************************************** -->
				495	<div class="doc_section">
				496	<a name="common">Helpful Hints for Common Operations</a>
				497	</div>
				498	<!-- *********************************************************************** -->
				499
				500	<div class="doc_text">
				501
				502	<p>This section describes how to perform some very simple transformations of
				503	LLVM code. This is meant to give examples of common idioms used, showing the
				504	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				505	you should also read about the main classes that you will be working with. The
				506	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				507	and descriptions of the main classes that you should know about.</p>
				508
				509	</div>
				510
				511	<!-- NOTE: this section should be heavy on example code -->
				512	<!-- ======================================================================= -->
				513	<div class="doc_subsection">
				514	<a name="inspection">Basic Inspection and Traversal Routines</a>
				515	</div>
				516
				517	<div class="doc_text">
				518
				519	<p>The LLVM compiler infrastructure have many different data structures that may
				520	be traversed. Following the example of the C++ standard template library, the
				521	techniques used to traverse these various data structures are all basically the
				522	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				523	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				524	function returns an iterator pointing to one past the last valid element of the
				525	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				526	between the two operations.</p>
				527
				528	<p>Because the pattern for iteration is common across many different aspects of
				529	the program representation, the standard template library algorithms may be used
				530	on them, and it is easier to remember how to iterate. First we show a few common
				531	examples of the data structures that need to be traversed. Other data
				532	structures are traversed in very similar ways.</p>
				533
				534	</div>
				535
				536	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	537	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	538	<a name="iterate_function">Iterating over the </a><a
				539	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				540	href="#Function"><tt>Function</tt></a>
				541	</div>
				542
				543	<div class="doc_text">
				544
				545	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				546	transform in some way; in particular, you'd like to manipulate its
				547	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				548	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				549	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				550	<tt>Instruction</tt>s it contains:</p>
				551
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	552	<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]	553
				554	<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]	555	invoking member functions of the <tt>Instruction</tt> class. This is
				556	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	557	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	558	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				559
				560	</div>
				561
				562	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	563	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	564	<a name="iterate_basicblock">Iterating over the </a><a
				565	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				566	href="#BasicBlock"><tt>BasicBlock</tt></a>
				567	</div>
				568
				569	<div class="doc_text">
				570
				571	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				572	easy to iterate over the individual instructions that make up
				573	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				574	a <tt>BasicBlock</tt>:</p>
				575
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	576	<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]	577
				578	<p>However, this isn't really the best way to print out the contents of a
				579	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				580	anything you'll care about, you could have just invoked the print routine on the
				581	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				582
				583	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				584	it will print out the contents of the pointer, instead of the pointer value you
				585	might expect. This is a deprecated interface that will be removed in the
				586	future, so it's best not to depend on it. To print out the pointer value for
				587	now, you must cast to <tt>void*</tt>.</p>
				588
				589	</div>
				590
				591	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	592	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	593	<a name="iterate_institer">Iterating over the </a><a
				594	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				595	href="#Function"><tt>Function</tt></a>
				596	</div>
				597
				598	<div class="doc_text">
				599
				600	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				601	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				602	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				603	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				604	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]	605	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]	606
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	607	<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]	608	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				609	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	610	initialize a worklist to contain all instructions in a <tt>Function</tt>
				611	F, all you would need to do is something like:
				612	<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]	613
				614	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				615	<tt>Function</tt> pointed to by F.</p>
				616
				617	</div>
				618
				619	<!-- _______________________________________________________________________ -->
				620	<div class="doc_subsubsection">
				621	<a name="iterate_convert">Turning an iterator into a class pointer (and
				622	vice-versa)</a>
				623	</div>
				624
				625	<div class="doc_text">
				626
				627	<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]	628	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]	629	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	630	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]	631	is a <tt>BasicBlock::const_iterator</tt>:</p>
				632
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	633	<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]	634
				635	<p>However, the iterators you'll be working with in the LLVM framework are
				636	special: they will automatically convert to a ptr-to-instance type whenever they
				637	need to. Instead of dereferencing the iterator and then taking the address of
				638	the result, you can simply assign the iterator to the proper pointer type and
				639	you get the dereference and address-of operation as a result of the assignment
				640	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				641	the last line of the last example,</p>
				642
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	643	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	644
				645	<p>is semantically equivalent to</p>
				646
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	647	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	648
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	649	<p>It's also possible to turn a class pointer into the corresponding iterator,
				650	and this is a constant time operation (very efficient). The following code
				651	snippet illustrates use of the conversion constructors provided by LLVM
				652	iterators. By using these, you can explicitly grab the iterator of something
				653	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	654
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	655	<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]	656
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	657	</div>
				658
				659	<!--_______________________________________________________________________-->
				660	<div class="doc_subsubsection">
				661	<a name="iterate_complex">Finding call sites: a slightly more complex
				662	example</a>
				663	</div>
				664
				665	<div class="doc_text">
				666
				667	<p>Say that you're writing a FunctionPass and would like to count all the
				668	locations in the entire module (that is, across every <tt>Function</tt>) where a
				669	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				670	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]	671	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]	672	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				673	is what we want to do:</p>
				674
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	675	<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]	676
				677	<p>And the actual code is (remember, since we're writing a
				678	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				679	override the <tt>runOnFunction</tt> method...):</p>
				680
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	681	<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
				682	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				683	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]	684
				685	</div>
				686
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	687	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	688	<div class="doc_subsubsection">
				689	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				690	</div>
				691
				692	<div class="doc_text">
				693
				694	<p>You may have noticed that the previous example was a bit oversimplified in
				695	that it did not deal with call sites generated by 'invoke' instructions. In
				696	this, and in other situations, you may find that you want to treat
				697	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				698	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				699	less closely-related things. For these cases, LLVM provides a handy wrapper
				700	class called <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	701	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]	702	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				703	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	704	<tt>InvokeInst</tt>s.</p>
				705
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	706	<p>This class has "value semantics": it should be passed by value, not by
				707	reference and it should not be dynamically allocated or deallocated using
				708	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				709	assignable and constructable, with costs equivalents to that of a bare pointer.
				710	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]	711
				712	</div>
				713
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	714	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	715	<div class="doc_subsubsection">
				716	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				717	</div>
				718
				719	<div class="doc_text">
				720
				721	<p>Frequently, we might have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	722	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				723	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				724	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				725	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				726	particular function <tt>foo</tt>. Finding all of the instructions that
				727	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				728	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	729
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	730	<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]	731
				732	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	733	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]	734	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				735	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				736	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				737	all of the values that a particular instruction uses (that is, the operands of
				738	the particular <tt>Instruction</tt>):</p>
				739
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	740	<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]	741
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	742	<!--
				743	def-use chains ("finding all users of"): Value::use_begin/use_end
				744	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]	745	-->
				746
				747	</div>
				748
				749	<!-- ======================================================================= -->
				750	<div class="doc_subsection">
				751	<a name="simplechanges">Making simple changes</a>
				752	</div>
				753
				754	<div class="doc_text">
				755
				756	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	757	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	758	transformations, it's fairly common to manipulate the contents of basic
				759	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	760	and gives example code.</p>
				761
				762	</div>
				763
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	764	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	765	<div class="doc_subsubsection">
				766	<a name="schanges_creating">Creating and inserting new
				767	<tt>Instruction</tt>s</a>
				768	</div>
				769
				770	<div class="doc_text">
				771
				772	<p><i>Instantiating Instructions</i></p>
				773
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	774	<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]	775	constructor for the kind of instruction to instantiate and provide the necessary
				776	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				777	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				778
				779	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				780
				781	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				782	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				783	subclass is likely to have varying default parameters which change the semantics
				784	of the instruction, so refer to the <a
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	785	href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	786	Instruction</a> that you're interested in instantiating.</p>
				787
				788	<p><i>Naming values</i></p>
				789
				790	<p>It is very useful to name the values of instructions when you're able to, as
				791	this facilitates the debugging of your transformations. If you end up looking
				792	at generated LLVM machine code, you definitely want to have logical names
				793	associated with the results of instructions! By supplying a value for the
				794	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				795	associate a logical name with the result of the instruction's execution at
				796	runtime. For example, say that I'm writing a transformation that dynamically
				797	allocates space for an integer on the stack, and that integer is going to be
				798	used as some kind of index by some other code. To accomplish this, I place an
				799	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				800	<tt>Function</tt>, and I'm intending to use it within the same
				801	<tt>Function</tt>. I might do:</p>
				802
				803	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				804
				805	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				806	execution value, which is a pointer to an integer on the runtime stack.</p>
				807
				808	<p><i>Inserting instructions</i></p>
				809
				810	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				811	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				812
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	813	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	814	<li>Insertion into an explicit instruction list
				815
				816	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				817	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				818	before <tt>*pi</tt>, we do the following: </p>
				819
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	820	<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>
				821
				822	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				823	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				824	classes provide constructors which take a pointer to a
				825	<tt>BasicBlock</tt> to be appended to. For example code that
				826	looked like: </p>
				827
				828	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				829
				830	<p>becomes: </p>
				831
				832	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				833
				834	<p>which is much cleaner, especially if you are creating
				835	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	836
				837	<li>Insertion into an implicit instruction list
				838
				839	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				840	are implicitly associated with an existing instruction list: the instruction
				841	list of the enclosing basic block. Thus, we could have accomplished the same
				842	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				843	</p>
				844
				845	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				846
				847	<p>In fact, this sequence of steps occurs so frequently that the
				848	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				849	constructors which take (as a default parameter) a pointer to an
				850	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				851	precede. That is, <tt>Instruction</tt> constructors are capable of
				852	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				853	provided instruction, immediately before that instruction. Using an
				854	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				855	parameter, the above code becomes:</p>
				856
				857	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				858
				859	<p>which is much cleaner, especially if you're creating a lot of
				860	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				861	</ul>
				862
				863	</div>
				864
				865	<!--_______________________________________________________________________-->
				866	<div class="doc_subsubsection">
				867	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				868	</div>
				869
				870	<div class="doc_text">
				871
				872	<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]	873	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	874	you must have a pointer to the instruction that you wish to delete. Second, you
				875	need to obtain the pointer to that instruction's basic block. You use the
				876	pointer to the basic block to get its list of instructions and then use the
				877	erase function to remove your instruction. For example:</p>
				878
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	879	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				880	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]	881
				882	</div>
				883
				884	<!--_______________________________________________________________________-->
				885	<div class="doc_subsubsection">
				886	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				887	<tt>Value</tt></a>
				888	</div>
				889
				890	<div class="doc_text">
				891
				892	<p><i>Replacing individual instructions</i></p>
				893
				894	<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]	895	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	896	and <tt>ReplaceInstWithInst</tt>.</p>
				897
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	898	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	899
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	900	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	901	<li><tt>ReplaceInstWithValue</tt>
				902
				903	<p>This function replaces all uses (within a basic block) of a given
				904	instruction with a value, and then removes the original instruction. The
				905	following example illustrates the replacement of the result of a particular
				906	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				907	pointer to an integer.</p>
				908
				909	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				910
				911	<li><tt>ReplaceInstWithInst</tt>
				912
				913	<p>This function replaces a particular instruction with another
				914	instruction. The following example illustrates the replacement of one
				915	<tt>AllocaInst</tt> with another.</p>
				916
				917	<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]	918	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	919
				920	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				921
				922	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				923	<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]	924	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				925	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]	926	information.</p>
				927
				928	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				929	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				930	ReplaceInstWithValue, ReplaceInstWithInst -->
				931
				932	</div>
				933
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	934	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	935	<div class="doc_section">
				936	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				937	</div>
				938	<!-- *********************************************************************** -->
				939
				940	<div class="doc_text">
				941
				942	<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]	943	being inspected or transformed. The core LLVM classes are defined in
				944	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	945	the <tt>lib/VMCore</tt> directory.</p>
				946
				947	</div>
				948
				949	<!-- ======================================================================= -->
				950	<div class="doc_subsection">
				951	<a name="Value">The <tt>Value</tt> class</a>
				952	</div>
				953
				954	<div>
				955
				956	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				957	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	958	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]	959
				960	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				961	base. It represents a typed value that may be used (among other things) as an
				962	operand to an instruction. There are many different types of <tt>Value</tt>s,
				963	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				964	href="#Argument"><tt>Argument</tt></a>s. Even <a
				965	href="#Instruction"><tt>Instruction</tt></a>s and <a
				966	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				967
				968	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				969	for a program. For example, an incoming argument to a function (represented
				970	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				971	every instruction in the function that references the argument. To keep track
				972	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				973	href="#User"><tt>User</tt></a>s that is using it (the <a
				974	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				975	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				976	def-use information in the program, and is accessible through the <tt>use_</tt>*
				977	methods, shown below.</p>
				978
				979	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				980	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				981	method. In addition, all LLVM values can be named. The "name" of the
				982	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				983
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	984	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	985
				986	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				987	that the name of any value may be missing (an empty string), so names should
				988	<b>ONLY</b> be used for debugging (making the source code easier to read,
				989	debugging printouts), they should not be used to keep track of values or map
				990	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				991	<tt>Value</tt> itself instead.</p>
				992
				993	<p>One important aspect of LLVM is that there is no distinction between an SSA
				994	variable and the operation that produces it. Because of this, any reference to
				995	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]	996	argument, for example) is represented as a direct pointer to the instance of
				997	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	998	represents this value. Although this may take some getting used to, it
				999	simplifies the representation and makes it easier to manipulate.</p>
				1000
				1001	</div>
				1002
				1003	<!-- _______________________________________________________________________ -->
				1004	<div class="doc_subsubsection">
				1005	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				1006	</div>
				1007
				1008	<div class="doc_text">
				1009
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1010	<ul>
				1011	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1012	use-list<br>
				1013	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1014	the use-list<br>
				1015	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1016	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1017	<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]	1018	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1019	the use-list.<br>
				1020	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1021	use-list.<br>
				1022	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1023	element in the list.
				1024	<p> These methods are the interface to access the def-use
				1025	information in LLVM. As with all other iterators in LLVM, the naming
				1026	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]	1027	</li>
				1028	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1029	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1030	</li>
				1031	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1032	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1033	<tt>void setName(const std::string &Name)</tt>
				1034	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1035	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1036	</li>
				1037	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1038
				1039	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1040	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1041	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1042	produces a constant value (for example through constant folding), you can
				1043	replace all uses of the instruction with the constant like this:</p>
				1044
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1045	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1046	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1047
				1048	</div>
				1049
				1050	<!-- ======================================================================= -->
				1051	<div class="doc_subsection">
				1052	<a name="User">The <tt>User</tt> class</a>
				1053	</div>
				1054
				1055	<div class="doc_text">
				1056
				1057	<p>
				1058	<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]	1059	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]	1060	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1061
				1062	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1063	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1064	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1065	referring to. The <tt>User</tt> class itself is a subclass of
				1066	<tt>Value</tt>.</p>
				1067
				1068	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1069	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1070	Single Assignment (SSA) form, there can only be one definition referred to,
				1071	allowing this direct connection. This connection provides the use-def
				1072	information in LLVM.</p>
				1073
				1074	</div>
				1075
				1076	<!-- _______________________________________________________________________ -->
				1077	<div class="doc_subsubsection">
				1078	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1079	</div>
				1080
				1081	<div class="doc_text">
				1082
				1083	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1084	an index access interface and through an iterator based interface.</p>
				1085
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1086	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1087	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1088	<tt>unsigned getNumOperands()</tt>
				1089	<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]	1090	convenient form for direct access.</p></li>
				1091
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1092	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1093	list<br>
				1094	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1095	Get an iterator to the start of the operand list.<br>
				1096	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1097	operand list.
				1098	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1099	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1100	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1101
				1102	</div>
				1103
				1104	<!-- ======================================================================= -->
				1105	<div class="doc_subsection">
				1106	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1107	</div>
				1108
				1109	<div class="doc_text">
				1110
				1111	<p><tt>#include "</tt><tt><a
				1112	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1113	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]	1114	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1115	href="#Value"><tt>Value</tt></a></p>
				1116
				1117	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1118	instructions. It provides only a few methods, but is a very commonly used
				1119	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1120	opcode (instruction type) and the parent <a
				1121	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1122	into. To represent a specific type of instruction, one of many subclasses of
				1123	<tt>Instruction</tt> are used.</p>
				1124
				1125	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1126	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1127	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1128	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1129	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1130	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1131	file contains some meta-data about the various different types of instructions
				1132	in LLVM. It describes the enum values that are used as opcodes (for example
				1133	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1134	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1135	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1136	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1137	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]	1138	<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1139
				1140	</div>
				1141
				1142	<!-- _______________________________________________________________________ -->
				1143	<div class="doc_subsubsection">
				1144	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1145	class</a>
				1146	</div>
				1147
				1148	<div class="doc_text">
				1149
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1150	<ul>
				1151	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1152	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1153	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1154	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1155	<p>Returns true if the instruction writes to memory, i.e. it is a
				1156	<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]	1157	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1158	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1159	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1160	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1161	in all ways to the original except that the instruction has no parent
				1162	(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]	1163	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1164	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1165
				1166	</div>
				1167
				1168	<!-- ======================================================================= -->
				1169	<div class="doc_subsection">
				1170	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1171	</div>
				1172
				1173	<div class="doc_text">
				1174
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1175	<p><tt>#include "<a
				1176	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1177	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1178	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1179	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1180
				1181	<p>This class represents a single entry multiple exit section of the code,
				1182	commonly known as a basic block by the compiler community. The
				1183	<tt>BasicBlock</tt> class maintains a list of <a
				1184	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1185	Matching the language definition, the last element of this list of instructions
				1186	is always a terminator instruction (a subclass of the <a
				1187	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1188
				1189	<p>In addition to tracking the list of instructions that make up the block, the
				1190	<tt>BasicBlock</tt> class also keeps track of the <a
				1191	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1192
				1193	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1194	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1195	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1196	<tt>label</tt>.</p>
				1197
				1198	</div>
				1199
				1200	<!-- _______________________________________________________________________ -->
				1201	<div class="doc_subsubsection">
				1202	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1203	class</a>
				1204	</div>
				1205
				1206	<div class="doc_text">
				1207
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1208	<ul>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1209
				1210	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1211	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1212
				1213	<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1214	insertion into a function. The constructor optionally takes a name for the new
				1215	block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
				1216	the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
				1217	automatically inserted at the end of the specified <a
				1218	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1219	manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
				1220
				1221	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1222	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1223	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1224	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt> -
				1225	STL-style functions for accessing the instruction list.
				1226
				1227	<p>These methods and typedefs are forwarding functions that have the same
				1228	semantics as the standard library methods of the same names. These methods
				1229	expose the underlying instruction list of a basic block in a way that is easy to
				1230	manipulate. To get the full complement of container operations (including
				1231	operations to update the list), you must use the <tt>getInstList()</tt>
				1232	method.</p></li>
				1233
				1234	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1235
				1236	<p>This method is used to get access to the underlying container that actually
				1237	holds the Instructions. This method must be used when there isn't a forwarding
				1238	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1239	to perform. Because there are no forwarding functions for "updating"
				1240	operations, you need to use this if you want to update the contents of a
				1241	<tt>BasicBlock</tt>.</p></li>
				1242
				1243	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1244
				1245	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1246	embedded into, or a null pointer if it is homeless.</p></li>
				1247
				1248	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1249
				1250	<p> Returns a pointer to the terminator instruction that appears at the end of
				1251	the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1252	instruction in the block is not a terminator, then a null pointer is
				1253	returned.</p></li>
				1254
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1255	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1256
				1257	</div>
				1258
				1259	<!-- ======================================================================= -->
				1260	<div class="doc_subsection">
				1261	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1262	</div>
				1263
				1264	<div class="doc_text">
				1265
				1266	<p><tt>#include "<a
				1267	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1268	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1269	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1270	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1271	href="#Value"><tt>Value</tt></a></p>
				1272
				1273	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1274	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1275	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1276	Because they are visible at global scope, they are also subject to linking with
				1277	other globals defined in different translation units. To control the linking
				1278	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1279	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1280	defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1281
				1282	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1283	<tt>static</tt> in C), it is not visible to code outside the current translation
				1284	unit, and does not participate in linking. If it has external linkage, it is
				1285	visible to external code, and does participate in linking. In addition to
				1286	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1287	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1288
				1289	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1290	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1291	global is always a pointer to its contents. It is important to remember this
				1292	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1293	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1294	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1295	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1296	the address of the first element of this array and the value of the
				1297	<tt>GlobalVariable</tt> are the same, they have different types. The
				1298	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1299	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1300	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1301	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1302	Language Reference Manual</a>.</p>
				1303
				1304	</div>
				1305
				1306	<!-- _______________________________________________________________________ -->
				1307	<div class="doc_subsubsection">
				1308	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1309	class</a>
				1310	</div>
				1311
				1312	<div class="doc_text">
				1313
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1314	<ul>
				1315	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1316	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1317	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1318	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1319	<p> </p>
				1320	</li>
				1321	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1322	<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]	1323	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1324	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1325
				1326	</div>
				1327
				1328	<!-- ======================================================================= -->
				1329	<div class="doc_subsection">
				1330	<a name="Function">The <tt>Function</tt> class</a>
				1331	</div>
				1332
				1333	<div class="doc_text">
				1334
				1335	<p><tt>#include "<a
				1336	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]	1337	info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
				1338	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1339	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1340
				1341	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1342	actually one of the more complex classes in the LLVM heirarchy because it must
				1343	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1344	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1345	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1346	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1347
				1348	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1349	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1350	ordering of the blocks in the function, which indicate how the code will be
				1351	layed out by the backend. Additionally, the first <a
				1352	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1353	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1354	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1355	nodes from a single <tt>Function</tt>. If the <a
				1356	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1357	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1358	function hasn't been linked in yet.</p>
				1359
				1360	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1361	<tt>Function</tt> class also keeps track of the list of formal <a
				1362	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1363	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1364	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1365	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1366
				1367	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1368	LLVM feature that is only used when you have to look up a value by name. Aside
				1369	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1370	internally to make sure that there are not conflicts between the names of <a
				1371	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1372	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1373	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1374
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1375	<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
				1376	and therefore also a <a href="#Constant">Constant</a>. The value of the function
				1377	is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1378	</div>
				1379
				1380	<!-- _______________________________________________________________________ -->
				1381	<div class="doc_subsubsection">
				1382	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1383	class</a>
				1384	</div>
				1385
				1386	<div class="doc_text">
				1387
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1388	<ul>
				1389	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1390	Ty, LinkageTypes Linkage, const std::string &N = "", Module Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1391
				1392	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1393	the the program. The constructor must specify the type of the function to
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1394	create and what type of linkage the function should have. The <a
				1395	href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1396	specifies the formal arguments and return value for the function. The same
				1397	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1398	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1399	in which the function is defined. If this argument is provided, the function
				1400	will automatically be inserted into that module's list of
				1401	functions.</p></li>
				1402
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1403	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1404
				1405	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1406	function is "external", it does not have a body, and thus must be resolved
				1407	by linking with a function defined in a different translation unit.</p></li>
				1408
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1409	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1410	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1411
				1412	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1413	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1414
				1415	<p>These are forwarding methods that make it easy to access the contents of
				1416	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1417	list.</p></li>
				1418
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1419	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1420
				1421	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1422	is necessary to use when you need to update the list or perform a complex
				1423	action that doesn't have a forwarding method.</p></li>
				1424
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1425	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1426	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1427	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1428
				1429	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1430	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1431
				1432	<p>These are forwarding methods that make it easy to access the contents of
				1433	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1434	list.</p></li>
				1435
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1436	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1437
				1438	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1439	necessary to use when you need to update the list or perform a complex
				1440	action that doesn't have a forwarding method.</p></li>
				1441
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1442	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1443
				1444	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1445	function. Because the entry block for the function is always the first
				1446	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1447
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1448	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1449	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1450
				1451	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1452	<tt>Function</tt> and returns the return type of the function, or the <a
				1453	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1454	function.</p></li>
				1455
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1456	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1457
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1458	<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]	1459	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1460	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1461
				1462	</div>
				1463
				1464	<!-- ======================================================================= -->
				1465	<div class="doc_subsection">
				1466	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1467	</div>
				1468
				1469	<div class="doc_text">
				1470
				1471	<p><tt>#include "<a
				1472	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1473	<br>
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1474	doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1475	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1476	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1477
				1478	<p>Global variables are represented with the (suprise suprise)
				1479	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1480	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1481	always referenced by their address (global values must live in memory, so their
				1482	"name" refers to their address). See <a
				1483	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1484	may have an initial value (which must be a <a
				1485	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1486	may be marked as "constant" themselves (indicating that their contents never
				1487	change at runtime).</p>
				1488
				1489	</div>
				1490
				1491	<!-- _______________________________________________________________________ -->
				1492	<div class="doc_subsubsection">
				1493	<a name="m_GlobalVariable">Important Public Members of the
				1494	<tt>GlobalVariable</tt> class</a>
				1495	</div>
				1496
				1497	<div class="doc_text">
				1498
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1499	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1500	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1501	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1502	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1503
				1504	<p>Create a new global variable of the specified type. If
				1505	<tt>isConstant</tt> is true then the global variable will be marked as
				1506	unchanging for the program. The Linkage parameter specifies the type of
				1507	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1508	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1509	the resultant global variable will have internal linkage. AppendingLinkage
				1510	concatenates together all instances (in different translation units) of the
				1511	variable into a single variable but is only applicable to arrays.  See
				1512	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1513	further details on linkage types. Optionally an initializer, a name, and the
				1514	module to put the variable into may be specified for the global variable as
				1515	well.</p></li>
				1516
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1517	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1518
				1519	<p>Returns true if this is a global variable that is known not to
				1520	be modified at runtime.</p></li>
				1521
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1522	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1523
				1524	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1525
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1526	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1527
				1528	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1529	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1530	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1531
				1532	</div>
				1533
				1534	<!-- ======================================================================= -->
				1535	<div class="doc_subsection">
				1536	<a name="Module">The <tt>Module</tt> class</a>
				1537	</div>
				1538
				1539	<div class="doc_text">
				1540
				1541	<p><tt>#include "<a
				1542	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1543	<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1544
				1545	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1546	programs. An LLVM module is effectively either a translation unit of the
				1547	original program or a combination of several translation units merged by the
				1548	linker. The <tt>Module</tt> class keeps track of a list of <a
				1549	href="#Function"><tt>Function</tt></a>s, a list of <a
				1550	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1551	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1552	helpful member functions that try to make common operations easy.</p>
				1553
				1554	</div>
				1555
				1556	<!-- _______________________________________________________________________ -->
				1557	<div class="doc_subsubsection">
				1558	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1559	</div>
				1560
				1561	<div class="doc_text">
				1562
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1563	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1564	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1565	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1566
				1567	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1568	provide a name for it (probably based on the name of the translation unit).</p>
				1569
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1570	<ul>
				1571	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1572	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1573
				1574	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1575	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1576
				1577	<p>These are forwarding methods that make it easy to access the contents of
				1578	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1579	list.</p></li>
				1580
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1581	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1582
				1583	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1584	necessary to use when you need to update the list or perform a complex
				1585	action that doesn't have a forwarding method.</p>
				1586
				1587	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1588	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1589
				1590	<hr>
				1591
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1592	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1593	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1594
				1595	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1596
				1597	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1598	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1599
				1600	<p> These are forwarding methods that make it easy to access the contents of
				1601	a <tt>Module</tt> object's <a
				1602	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1603
				1604	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1605
				1606	<p>Returns the list of <a
				1607	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1608	use when you need to update the list or perform a complex action that
				1609	doesn't have a forwarding method.</p>
				1610
				1611	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1612	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1613
				1614	<hr>
				1615
				1616	<ul>
				1617	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1618
				1619	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1620	for this <tt>Module</tt>.</p>
				1621
				1622	<p><!-- Convenience methods --></p></li>
				1623	</ul>
				1624
				1625	<hr>
				1626
				1627	<ul>
				1628	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1629	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1630
				1631	<p>Look up the specified function in the <tt>Module</tt> <a
				1632	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1633	<tt>null</tt>.</p></li>
				1634
				1635	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1636	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1637
				1638	<p>Look up the specified function in the <tt>Module</tt> <a
				1639	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1640	external declaration for the function and return it.</p></li>
				1641
				1642	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1643
				1644	<p>If there is at least one entry in the <a
				1645	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1646	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1647	string.</p></li>
				1648
				1649	<li><tt>bool addTypeName(const std::string &Name, const <a
				1650	href="#Type">Type</a> *Ty)</tt>
				1651
				1652	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1653	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1654	name, true is returned and the <a
				1655	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1656	</ul>
				1657
				1658	</div>
				1659
				1660	<!-- ======================================================================= -->
				1661	<div class="doc_subsection">
				1662	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1663	</div>
				1664
				1665	<div class="doc_text">
				1666
				1667	<p>Constant represents a base class for different types of constants. It
				1668	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1669	ConstantArray etc for representing the various types of Constants.</p>
				1670
				1671	</div>
				1672
				1673	<!-- _______________________________________________________________________ -->
				1674	<div class="doc_subsubsection">
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1675	<a name="m_Constant">Important Public Methods</a>
				1676	</div>
				1677	<div class="doc_text">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1678	</div>
				1679
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1680	<!-- _______________________________________________________________________ -->
				1681	<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1682	<div class="doc_text">
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1683	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1684	<li>ConstantSInt : This subclass of Constant represents a signed integer
				1685	constant.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1686	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1687	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1688	this constant. </li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1689	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1690	</li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1691	<li>ConstantUInt : This class represents an unsigned integer.
				1692	<ul>
				1693	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
				1694	this constant. </li>
				1695	</ul>
				1696	</li>
				1697	<li>ConstantFP : This class represents a floating point constant.
				1698	<ul>
				1699	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1700	this constant. </li>
				1701	</ul>
				1702	</li>
				1703	<li>ConstantBool : This represents a boolean constant.
				1704	<ul>
				1705	<li><tt>bool getValue() const</tt>: Returns the underlying value of this
				1706	constant. </li>
				1707	</ul>
				1708	</li>
				1709	<li>ConstantArray : This represents a constant array.
				1710	<ul>
				1711	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
				1712	a Vecotr of component constants that makeup this array. </li>
				1713	</ul>
				1714	</li>
				1715	<li>ConstantStruct : This represents a constant struct.
				1716	<ul>
				1717	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
				1718	a Vector of component constants that makeup this array. </li>
				1719	</ul>
				1720	</li>
				1721	<li>GlobalValue : This represents either a global variable or a function. In
				1722	either case, the value is a constant fixed address (after linking).
				1723	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1724	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1725	</div>
				1726
				1727	<!-- ======================================================================= -->
				1728	<div class="doc_subsection">
				1729	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1730	</div>
				1731
				1732	<div class="doc_text">
				1733
				1734	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1735	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1736	types are instances of subclasses of type like FunctionType, ArrayType
				1737	etc. DerivedType is the interface for all such dervied types including
				1738	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1739	be recursive (StructType). There exists exactly one instance of any type
				1740	structure at a time. This allows using pointer equality of Type *s for comparing
				1741	types.</p>
				1742
				1743	</div>
				1744
				1745	<!-- _______________________________________________________________________ -->
				1746	<div class="doc_subsubsection">
				1747	<a name="m_Value">Important Public Methods</a>
				1748	</div>
				1749
				1750	<div class="doc_text">
				1751
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1752	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1753
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1754	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1755	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1756	not true for Float and Double. </li>
				1757
				1758	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1759	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1760	return false as they do with isSigned. This returns true for UByteTy,
				1761	UShortTy, UIntTy, and ULongTy. </li>
				1762
Chris Lattner	4573f1b	2004-07-08 17:49:37 +0000	[diff] [blame]	1763	<li><tt>bool isInteger() const</tt>: Equivalent to isSigned() \|\| isUnsigned().</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1764
				1765	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1766	type, which is either Bool type or one of the Integer types.</li>
				1767
				1768	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1769	floating point types.</li>
				1770
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1771	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1772	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]	1773	example, uint to int or one pointer type to another.</li>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1774	</ul>
				1775	</div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1776
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1777	<!-- _______________________________________________________________________ -->
				1778	<div class="doc_subsubsection">
				1779	<a name="m_Value">Important Derived Types</a>
				1780	</div>
				1781	<div class="doc_text">
				1782	<ul>
				1783	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1784	<ul>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1785	<li><tt>const Type * getElementType() const</tt>: Returns the type of each
				1786	of the elements in the sequential type. </li>
				1787	</ul>
				1788	</li>
				1789	<li>ArrayType : This is a subclass of SequentialType and defines interface for
				1790	array types.
				1791	<ul>
				1792	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1793	elements in the array. </li>
				1794	</ul>
				1795	</li>
				1796	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1797	<li>StructType : subclass of DerivedTypes for struct types </li>
				1798	<li>FunctionType : subclass of DerivedTypes for function types.
				1799	<ul>
				1800	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1801	function</li>
				1802	<li><tt> const Type * getReturnType() const</tt>: Returns the
				1803	return type of the function.</li>
				1804	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
				1805	the type of the ith parameter.</li>
				1806	<li><tt> const unsigned getNumParams() const</tt>: Returns the
				1807	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1808	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1809	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1810	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1811	</div>
				1812
				1813	<!-- ======================================================================= -->
				1814	<div class="doc_subsection">
				1815	<a name="Argument">The <tt>Argument</tt> class</a>
				1816	</div>
				1817
				1818	<div class="doc_text">
				1819
				1820	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1821	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1822	arguments. An argument has a pointer to the parent Function.</p>
				1823
				1824	</div>
				1825
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1826	<!-- ======================================================================= -->
				1827	<div class="doc_subsection">
				1828	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1829	</div>
				1830	<div class="doc_text">
				1831	<p>This class provides a symbol table that the
				1832	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1833	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1834	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1835	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1836	type. It hides the data it contains and provides access to it through a
				1837	controlled interface.</p>
				1838
				1839	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1840	structure of the information it holds. The class contains two
				1841	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1842	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1843	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1844	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1845	however, are stored in a single dimension and accessed only by name.</p>
				1846
				1847	<p>The interface of this class provides three basic types of operations:
				1848	<ol>
				1849	<li><em>Accessors</em>. Accessors provide read-only access to information
				1850	such as finding a value for a name with the
				1851	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1852	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1853	<tt>SymbolTable</tt> with methods like
				1854	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1855	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1856	of the symbol table in well defined ways, such as the method
				1857	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1858	</ol>
				1859
				1860	<h3>Accessors</h3>
				1861	<dl>
				1862	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1863	</dt>
				1864	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1865	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1866	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1867
				1868	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1869	<dd>The <tt>lookupType</tt> method searches through the types for a
				1870	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1871	is not found, null is returned.</dd>
				1872
				1873	<dt><tt>bool hasTypes() const</tt>:</dt>
				1874	<dd>This function returns true if an entry has been made into the type
				1875	map.</dd>
				1876
				1877	<dt><tt>bool isEmpty() const</tt>:</dt>
				1878	<dd>This function returns true if both the value and types maps are
				1879	empty</dd>
				1880
				1881	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1882	<dd>This function returns the name of the Value provided or the empty
				1883	string if the Value is not in the symbol table.</dd>
				1884
				1885	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1886	<dd>This function returns the name of the Type provided or the empty
				1887	string if the Type is not in the symbol table.</dd>
				1888	</dl>
				1889
				1890	<h3>Mutators</h3>
				1891	<dl>
				1892	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1893	<dd>This method adds the provided value to the symbol table. The Value must
				1894	have both a name and a type which are extracted and used to place the value
				1895	in the correct type plane under the value's name.</dd>
				1896
				1897	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1898	<dd> Inserts a constant or type into the symbol table with the specified
				1899	name. There can be a many to one mapping between names and constants
				1900	or types.</dd>
				1901
				1902	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1903	<dd> Inserts a type into the symbol table with the specified name. There
				1904	can be a many-to-one mapping between names and types. This method
				1905	allows a type with an existing entry in the symbol table to get
				1906	a new name.</dd>
				1907
				1908	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1909	<dd> This method removes a named value from the symbol table. The
				1910	type and name of the Value are extracted from \p N and used to
				1911	lookup the Value in the correct type plane. If the Value is
				1912	not in the symbol table, this method silently ignores the
				1913	request.</dd>
				1914
				1915	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1916	<dd> This method removes a named type from the symbol table. The
				1917	name of the type is extracted from \P T and used to look up
				1918	the Type in the type map. If the Type is not in the symbol
				1919	table, this method silently ignores the request.</dd>
				1920
				1921	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1922	<dd> Remove a constant or type with the specified name from the
				1923	symbol table.</dd>
				1924
				1925	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1926	<dd> Remove a type with the specified name from the symbol table.
				1927	Returns the removed Type.</dd>
				1928
				1929	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1930	<dd> Removes a specific value from the symbol table.
				1931	Returns the removed value.</dd>
				1932
				1933	<dt><tt>bool strip()</tt>:</dt>
				1934	<dd> This method will strip the symbol table of its names leaving
				1935	the type and values. </dd>
				1936
				1937	<dt><tt>void clear()</tt>:</dt>
				1938	<dd>Empty the symbol table completely.</dd>
				1939	</dl>
				1940
				1941	<h3>Iteration</h3>
				1942	<p>The following functions describe three types of iterators you can obtain
				1943	the beginning or end of the sequence for both const and non-const. It is
				1944	important to keep track of the different kinds of iterators. There are
				1945	three idioms worth pointing out:</p>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1946	<table>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1947	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1948	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1949	<td align="left">Planes Of name/Value maps</td><td>PI</td>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1950	<td align="left"><pre><tt>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1951	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1952	PE = ST.plane_end(); PI != PE; ++PI ) {
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1953	PI->first // This is the Type* of the plane
				1954	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1955	</tt></pre></td>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1956	</tr>
				1957	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1958	<td align="left">All name/Type Pairs</td><td>TI</td>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1959	<td align="left"><pre><tt>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1960	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1961	TE = ST.type_end(); TI != TE; ++TI )
				1962	TI->first // This is the name of the type
				1963	TI->second // This is the Type* value associated with the name
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1964	</tt></pre></td>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1965	</tr>
				1966	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1967	<td align="left">name/Value pairs in a plane</td><td>VI</td>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1968	<td align="left"><pre><tt>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1969	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1970	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1971	VI->first // This is the name of the Value
				1972	VI->second // This is the Value* value associated with the name
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1973	</tt></pre></td>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1974	</tr>
				1975	</table>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1976
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1977	<p>Using the recommended iterator names and idioms will help you avoid
				1978	making mistakes. Of particular note, make sure that whenever you use
				1979	value_begin(SomeType) that you always compare the resulting iterator
				1980	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1981	will loop infinitely.</p>
				1982
				1983	<dl>
				1984
				1985	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1986	<dd>Get an iterator that starts at the beginning of the type planes.
				1987	The iterator will iterate over the Type/ValueMap pairs in the
				1988	type planes. </dd>
				1989
				1990	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1991	<dd>Get a const_iterator that starts at the beginning of the type
				1992	planes. The iterator will iterate over the Type/ValueMap pairs
				1993	in the type planes. </dd>
				1994
				1995	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1996	<dd>Get an iterator at the end of the type planes. This serves as
				1997	the marker for end of iteration over the type planes.</dd>
				1998
				1999	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				2000	<dd>Get a const_iterator at the end of the type planes. This serves as
				2001	the marker for end of iteration over the type planes.</dd>
				2002
				2003	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				2004	<dd>Get an iterator that starts at the beginning of a type plane.
				2005	The iterator will iterate over the name/value pairs in the type plane.
				2006	Note: The type plane must already exist before using this.</dd>
				2007
				2008	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				2009	<dd>Get a const_iterator that starts at the beginning of a type plane.
				2010	The iterator will iterate over the name/value pairs in the type plane.
				2011	Note: The type plane must already exist before using this.</dd>
				2012
				2013	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				2014	<dd>Get an iterator to the end of a type plane. This serves as the marker
				2015	for end of iteration of the type plane.
				2016	Note: The type plane must already exist before using this.</dd>
				2017
				2018	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				2019	<dd>Get a const_iterator to the end of a type plane. This serves as the
				2020	marker for end of iteration of the type plane.
				2021	Note: the type plane must already exist before using this.</dd>
				2022
				2023	<dt><tt>type_iterator type_begin()</tt>:</dt>
				2024	<dd>Get an iterator to the start of the name/Type map.</dd>
				2025
				2026	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				2027	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				2028
				2029	<dt><tt>type_iterator type_end()</tt>:</dt>
				2030	<dd>Get an iterator to the end of the name/Type map. This serves as the
				2031	marker for end of iteration of the types.</dd>
				2032
				2033	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2034	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2035	as the marker for end of iteration of the types.</dd>
				2036
				2037	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2038	<dd>This method returns a plane_const_iterator for iteration over
				2039	the type planes starting at a specific plane, given by \p Ty.</dd>
				2040
				2041	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2042	<dd>This method returns a plane_iterator for iteration over the
				2043	type planes starting at a specific plane, given by \p Ty.</dd>
				2044
				2045	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2046	<dd>This method returns a ValueMap* for a specific type plane. This
				2047	interface is deprecated and may go away in the future.</dd>
				2048	</dl>
				2049	</div>
				2050
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2051	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2052	<hr>
				2053	<address>
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				2058
				2059	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2060	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2061	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2062	Last modified: $Date$
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Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2065	</body>
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Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	2067	<!-- vim: sw=2 noai
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