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Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	3	<html>
				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">
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	7	</head>
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>
Chris Lattner	61db465	2004-12-08 19:05:44 +0000	[diff] [blame]	23
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	24	-->
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	25	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	26	</li>
				27	<li><a href="#apis">Important and useful LLVM APIs</a>
				28	<ul>
				29	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				30	and <tt>dyn_cast<></tt> templates</a> </li>
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	31	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	32	option</a>
				33	<ul>
				34	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				35	and the <tt>-debug-only</tt> option</a> </li>
				36	</ul>
				37	</li>
				38	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	39	option</a></li>
				40	<!--
				41	<li>The <tt>InstVisitor</tt> template
				42	<li>The general graph API
				43	-->
Chris Lattner	f623a08	2005-10-17 01:36:23 +0000	[diff] [blame]	44	<li><a href="#ViewGraph">Viewing graphs while debugging code</a></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	45	</ul>
				46	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	47	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	48	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	49	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				50	<ul>
				51	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				52	in a <tt>Function</tt></a> </li>
				53	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				54	in a <tt>BasicBlock</tt></a> </li>
				55	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				56	in a <tt>Function</tt></a> </li>
				57	<li><a href="#iterate_convert">Turning an iterator into a
				58	class pointer</a> </li>
				59	<li><a href="#iterate_complex">Finding call sites: a more
				60	complex example</a> </li>
				61	<li><a href="#calls_and_invokes">Treating calls and invokes
				62	the same way</a> </li>
				63	<li><a href="#iterate_chains">Iterating over def-use &
				64	use-def chains</a> </li>
				65	</ul>
				66	</li>
				67	<li><a href="#simplechanges">Making simple changes</a>
				68	<ul>
				69	<li><a href="#schanges_creating">Creating and inserting new
				70	<tt>Instruction</tt>s</a> </li>
				71	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				72	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				73	with another <tt>Value</tt></a> </li>
				74	</ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	75	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	76	<!--
				77	<li>Working with the Control Flow Graph
				78	<ul>
				79	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				80	<li>
				81	<li>
				82	</ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	83	-->
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	84	</ul>
				85	</li>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	86
				87	<li><a href="#advanced">Advanced Topics</a>
				88	<ul>
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	89	<li><a href="#TypeResolve">LLVM Type Resolution</a>
				90	<ul>
				91	<li><a href="#BuildRecType">Basic Recursive Type Construction</a></li>
				92	<li><a href="#refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a></li>
				93	<li><a href="#PATypeHolder">The PATypeHolder Class</a></li>
				94	<li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
				95	</ul></li>
				96
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	97	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				98	</ul></li>
				99
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	100	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	101	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	102	<li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	103	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	104	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	105	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	106	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
				107	<ul>
				108	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
				109	</ul>
				110	</li>
				111	<li><a href="#Module">The <tt>Module</tt> class</a></li>
				112	<li><a href="#Constant">The <tt>Constant</tt> class</a>
				113	<ul>
				114	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				115	<ul>
				116	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				117	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				118	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
				119	</ul>
				120	</li>
				121	</ul>
				122	</li>
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	123	</ul>
				124	</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	125	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	126	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	127	</ul>
				128	</li>
				129	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	130	</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	131	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	132
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	133	<div class="doc_author">
				134	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner	94c4359	2004-05-26 16:52:55 +0000	[diff] [blame]	135	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
				136	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
				137	<a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	138	</div>
				139
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	140	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	141	<div class="doc_section">
				142	<a name="introduction">Introduction </a>
				143	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	144	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	145
				146	<div class="doc_text">
				147
				148	<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]	149	interfaces available in the LLVM source-base. This manual is not
				150	intended to explain what LLVM is, how it works, and what LLVM code looks
				151	like. It assumes that you know the basics of LLVM and are interested
				152	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	153	code.</p>
				154
				155	<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]	156	way in the continuously growing source code that makes up the LLVM
				157	infrastructure. Note that this manual is not intended to serve as a
				158	replacement for reading the source code, so if you think there should be
				159	a method in one of these classes to do something, but it's not listed,
				160	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				161	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	162
				163	<p>The first section of this document describes general information that is
				164	useful to know when working in the LLVM infrastructure, and the second describes
				165	the Core LLVM classes. In the future this manual will be extended with
				166	information describing how to use extension libraries, such as dominator
				167	information, CFG traversal routines, and useful utilities like the <tt><a
				168	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				169
				170	</div>
				171
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	172	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	173	<div class="doc_section">
				174	<a name="general">General Information</a>
				175	</div>
				176	<!-- *********************************************************************** -->
				177
				178	<div class="doc_text">
				179
				180	<p>This section contains general information that is useful if you are working
				181	in the LLVM source-base, but that isn't specific to any particular API.</p>
				182
				183	</div>
				184
				185	<!-- ======================================================================= -->
				186	<div class="doc_subsection">
				187	<a name="stl">The C++ Standard Template Library</a>
				188	</div>
				189
				190	<div class="doc_text">
				191
				192	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	193	perhaps much more than you are used to, or have seen before. Because of
				194	this, you might want to do a little background reading in the
				195	techniques used and capabilities of the library. There are many good
				196	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]	197	can get, so it will not be discussed in this document.</p>
				198
				199	<p>Here are some useful links:</p>
				200
				201	<ol>
				202
				203	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				204	reference</a> - an excellent reference for the STL and other parts of the
				205	standard C++ library.</li>
				206
				207	<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]	208	O'Reilly book in the making. It has a decent
				209	Standard Library
				210	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]	211	published.</li>
				212
				213	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				214	Questions</a></li>
				215
				216	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				217	Contains a useful <a
				218	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				219	STL</a>.</li>
				220
				221	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				222	Page</a></li>
				223
Tanya Lattner	79445ba	2004-12-08 18:34:56 +0000	[diff] [blame]	224	<li><a href="http://64.78.49.204/">
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	225	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				226	the book).</a></li>
				227
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	228	</ol>
				229
				230	<p>You are also encouraged to take a look at the <a
				231	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				232	to write maintainable code more than where to put your curly braces.</p>
				233
				234	</div>
				235
				236	<!-- ======================================================================= -->
				237	<div class="doc_subsection">
				238	<a name="stl">Other useful references</a>
				239	</div>
				240
				241	<div class="doc_text">
				242
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	243	<ol>
				244	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	245	Branch and Tag Primer</a></li>
Misha Brukman	a0f71e4	2004-06-18 18:39:00 +0000	[diff] [blame]	246	<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
				247	static and shared libraries across platforms</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	248	</ol>
				249
				250	</div>
				251
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	252	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	253	<div class="doc_section">
				254	<a name="apis">Important and useful LLVM APIs</a>
				255	</div>
				256	<!-- *********************************************************************** -->
				257
				258	<div class="doc_text">
				259
				260	<p>Here we highlight some LLVM APIs that are generally useful and good to
				261	know about when writing transformations.</p>
				262
				263	</div>
				264
				265	<!-- ======================================================================= -->
				266	<div class="doc_subsection">
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	267	<a name="isa">The <tt>isa<></tt>, <tt>cast<></tt> and
				268	<tt>dyn_cast<></tt> templates</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	269	</div>
				270
				271	<div class="doc_text">
				272
				273	<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]	274	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				275	operator, but they don't have some drawbacks (primarily stemming from
				276	the fact that <tt>dynamic_cast<></tt> only works on classes that
				277	have a v-table). Because they are used so often, you must know what they
				278	do and how they work. All of these templates are defined in the <a
Chris Lattner	695b78b	2005-04-26 22:56:16 +0000	[diff] [blame]	279	href="/doxygen/Casting_8h-source.html"><tt>llvm/Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	280	file (note that you very rarely have to include this file directly).</p>
				281
				282	<dl>
				283	<dt><tt>isa<></tt>: </dt>
				284
				285	<dd>The <tt>isa<></tt> operator works exactly like the Java
				286	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				287	a reference or pointer points to an instance of the specified class. This can
				288	be very useful for constraint checking of various sorts (example below).</dd>
				289
				290	<dt><tt>cast<></tt>: </dt>
				291
				292	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				293	converts a pointer or reference from a base class to a derived cast, causing
				294	an assertion failure if it is not really an instance of the right type. This
				295	should be used in cases where you have some information that makes you believe
				296	that something is of the right type. An example of the <tt>isa<></tt>
				297	and <tt>cast<></tt> template is:
				298
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	299	<pre>
				300	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				301	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				302	return true;
				303
Chris Lattner	53f72b3	2005-04-22 04:49:59 +0000	[diff] [blame]	304	<i>// Otherwise, it must be an instruction...</i>
				305	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				306	}
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	307	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	308
				309	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				310	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				311	operator.</p>
				312
				313	</dd>
				314
				315	<dt><tt>dyn_cast<></tt>:</dt>
				316
				317	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				318	checks to see if the operand is of the specified type, and if so, returns a
				319	pointer to it (this operator does not work with references). If the operand is
				320	not of the correct type, a null pointer is returned. Thus, this works very
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	321	much like the <tt>dynamic_cast<></tt> operator in C++, and should be
				322	used in the same circumstances. Typically, the <tt>dyn_cast<></tt>
				323	operator is used in an <tt>if</tt> statement or some other flow control
				324	statement like this:
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	325
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	326	<pre>
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	327	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				328	...
				329	}
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	330	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	331
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	332	<p>This form of the <tt>if</tt> statement effectively combines together a call
				333	to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				334	statement, which is very convenient.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	335
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	336	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				337	<tt>dynamic_cast<></tt> or Java's <tt>instanceof</tt> operator, can be
				338	abused. In particular, you should not use big chained <tt>if/then/else</tt>
				339	blocks to check for lots of different variants of classes. If you find
				340	yourself wanting to do this, it is much cleaner and more efficient to use the
				341	<tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	342
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	343	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	344
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	345	<dt><tt>cast_or_null<></tt>: </dt>
				346
				347	<dd>The <tt>cast_or_null<></tt> operator works just like the
				348	<tt>cast<></tt> operator, except that it allows for a null pointer as an
				349	argument (which it then propagates). This can sometimes be useful, allowing
				350	you to combine several null checks into one.</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	351
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	352	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	353
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	354	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				355	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				356	as an argument (which it then propagates). This can sometimes be useful,
				357	allowing you to combine several null checks into one.</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	358
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	359	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	360
				361	<p>These five templates can be used with any classes, whether they have a
				362	v-table or not. To add support for these templates, you simply need to add
				363	<tt>classof</tt> static methods to the class you are interested casting
				364	to. Describing this is currently outside the scope of this document, but there
				365	are lots of examples in the LLVM source base.</p>
				366
				367	</div>
				368
				369	<!-- ======================================================================= -->
				370	<div class="doc_subsection">
Misha Brukman	2c122ce	2005-11-01 21:12:49 +0000	[diff] [blame]	371	<a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	372	</div>
				373
				374	<div class="doc_text">
				375
				376	<p>Often when working on your pass you will put a bunch of debugging printouts
				377	and other code into your pass. After you get it working, you want to remove
				378	it... but you may need it again in the future (to work out new bugs that you run
				379	across).</p>
				380
				381	<p> Naturally, because of this, you don't want to delete the debug printouts,
				382	but you don't want them to always be noisy. A standard compromise is to comment
				383	them out, allowing you to enable them if you need them in the future.</p>
				384
Chris Lattner	695b78b	2005-04-26 22:56:16 +0000	[diff] [blame]	385	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">llvm/Support/Debug.h</a></tt>"
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	386	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				387	this problem. Basically, you can put arbitrary code into the argument of the
				388	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				389	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				390
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	391	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	392
				393	<p>Then you can run your pass like this:</p>
				394
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	395	<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]	396
				397	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				398	to not have to create "yet another" command line option for the debug output for
				399	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				400	so they do not cause a performance impact at all (for the same reason, they
				401	should also not contain side-effects!).</p>
				402
				403	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				404	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				405	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				406	program hasn't been started yet, you can always just run it with
				407	<tt>-debug</tt>.</p>
				408
				409	</div>
				410
				411	<!-- _______________________________________________________________________ -->
				412	<div class="doc_subsubsection">
Chris Lattner	c915108	2005-04-26 22:57:07 +0000	[diff] [blame]	413	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	414	the <tt>-debug-only</tt> option</a>
				415	</div>
				416
				417	<div class="doc_text">
				418
				419	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				420	just turns on <b>too much</b> information (such as when working on the code
				421	generator). If you want to enable debug information with more fine-grained
				422	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				423	option as follows:</p>
				424
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	425	<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]	426
				427	<p>Then you can run your pass like this:</p>
				428
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	429	<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]	430
				431	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				432	a file, to specify the debug type for the entire module (if you do this before
Chris Lattner	695b78b	2005-04-26 22:56:16 +0000	[diff] [blame]	433	you <tt>#include "llvm/Support/Debug.h"</tt>, you don't have to insert the ugly
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	434	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				435	"bar", because there is no system in place to ensure that names do not
				436	conflict. If two different modules use the same string, they will all be turned
				437	on when the name is specified. This allows, for example, all debug information
				438	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	439	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	440
				441	</div>
				442
				443	<!-- ======================================================================= -->
				444	<div class="doc_subsection">
				445	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				446	option</a>
				447	</div>
				448
				449	<div class="doc_text">
				450
				451	<p>The "<tt><a
Chris Lattner	695b78b	2005-04-26 22:56:16 +0000	[diff] [blame]	452	href="/doxygen/Statistic_8h-source.html">llvm/ADT/Statistic.h</a></tt>" file
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	453	provides a template named <tt>Statistic</tt> that is used as a unified way to
				454	keep track of what the LLVM compiler is doing and how effective various
				455	optimizations are. It is useful to see what optimizations are contributing to
				456	making a particular program run faster.</p>
				457
				458	<p>Often you may run your pass on some big program, and you're interested to see
				459	how many times it makes a certain transformation. Although you can do this with
				460	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				461	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				462	keep track of this information, and the calculated information is presented in a
				463	uniform manner with the rest of the passes being executed.</p>
				464
				465	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				466	it are as follows:</p>
				467
				468	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	469	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	470	<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]	471
				472	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				473	but if you do not specify a template argument, it defaults to acting like
				474	an unsigned int counter (this is usually what you want).</p></li>
				475
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	476	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	477	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	478	</li>
				479	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	480
				481	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				482	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				483
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	484	<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]	485
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	486	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				487	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	488
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	489	<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]	490
				491	<p>Obviously, with so many optimizations, having a unified framework for this
				492	stuff is very nice. Making your pass fit well into the framework makes it more
				493	maintainable and useful.</p>
				494
				495	</div>
				496
Chris Lattner	f623a08	2005-10-17 01:36:23 +0000	[diff] [blame]	497	<!-- ======================================================================= -->
				498	<div class="doc_subsection">
				499	<a name="ViewGraph">Viewing graphs while debugging code</a>
				500	</div>
				501
				502	<div class="doc_text">
				503
				504	<p>Several of the important data structures in LLVM are graphs: for example
				505	CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
				506	LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
				507	<a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
				508	DAGs</a>. In many cases, while debugging various parts of the compiler, it is
				509	nice to instantly visualize these graphs.</p>
				510
				511	<p>LLVM provides several callbacks that are available in a debug build to do
				512	exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
				513	the current LLVM tool will pop up a window containing the CFG for the function
				514	where each basic block is a node in the graph, and each node contains the
				515	instructions in the block. Similarly, there also exists
				516	<tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
				517	<tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
				518	and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
Jim Laskey	543a0ee	2006-10-02 12:28:07 +0000	[diff] [blame^]	519	you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
Chris Lattner	f623a08	2005-10-17 01:36:23 +0000	[diff] [blame]	520	up a window. Alternatively, you can sprinkle calls to these functions in your
				521	code in places you want to debug.</p>
				522
				523	<p>Getting this to work requires a small amount of configuration. On Unix
				524	systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
				525	toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
				526	Mac OS/X, download and install the Mac OS/X <a
				527	href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
				528	<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
				529	it) to your path. Once in your system and path are set up, rerun the LLVM
				530	configure script and rebuild LLVM to enable this functionality.</p>
				531
Jim Laskey	543a0ee	2006-10-02 12:28:07 +0000	[diff] [blame^]	532	<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
				533	<i>interesting</i> nodes in large complex graphs. From gdb, if you
				534	<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
				535	next <tt>call DAG.viewGraph()</tt> would hilight the node in the
				536	specified color (choices of colors can be found at <a
				537	href="http://www.graphviz.org/doc/info/colors.html">Colors<a>.) More
				538	complex node attributes can be provided with <tt>call
				539	DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
				540	found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
				541	Attributes</a>.) If you want to restart and clear all the current graph
				542	attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
				543
Chris Lattner	f623a08	2005-10-17 01:36:23 +0000	[diff] [blame]	544	</div>
				545
				546
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	547	<!-- *********************************************************************** -->
				548	<div class="doc_section">
				549	<a name="common">Helpful Hints for Common Operations</a>
				550	</div>
				551	<!-- *********************************************************************** -->
				552
				553	<div class="doc_text">
				554
				555	<p>This section describes how to perform some very simple transformations of
				556	LLVM code. This is meant to give examples of common idioms used, showing the
				557	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				558	you should also read about the main classes that you will be working with. The
				559	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				560	and descriptions of the main classes that you should know about.</p>
				561
				562	</div>
				563
				564	<!-- NOTE: this section should be heavy on example code -->
				565	<!-- ======================================================================= -->
				566	<div class="doc_subsection">
				567	<a name="inspection">Basic Inspection and Traversal Routines</a>
				568	</div>
				569
				570	<div class="doc_text">
				571
				572	<p>The LLVM compiler infrastructure have many different data structures that may
				573	be traversed. Following the example of the C++ standard template library, the
				574	techniques used to traverse these various data structures are all basically the
				575	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				576	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				577	function returns an iterator pointing to one past the last valid element of the
				578	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				579	between the two operations.</p>
				580
				581	<p>Because the pattern for iteration is common across many different aspects of
				582	the program representation, the standard template library algorithms may be used
				583	on them, and it is easier to remember how to iterate. First we show a few common
				584	examples of the data structures that need to be traversed. Other data
				585	structures are traversed in very similar ways.</p>
				586
				587	</div>
				588
				589	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	590	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	591	<a name="iterate_function">Iterating over the </a><a
				592	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				593	href="#Function"><tt>Function</tt></a>
				594	</div>
				595
				596	<div class="doc_text">
				597
				598	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				599	transform in some way; in particular, you'd like to manipulate its
				600	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				601	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				602	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				603	<tt>Instruction</tt>s it contains:</p>
				604
Chris Lattner	ac5bb69	2005-11-28 02:30:22 +0000	[diff] [blame]	605	<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> std::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]	606
				607	<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]	608	invoking member functions of the <tt>Instruction</tt> class. This is
				609	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	610	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	611	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				612
				613	</div>
				614
				615	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	616	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	617	<a name="iterate_basicblock">Iterating over the </a><a
				618	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				619	href="#BasicBlock"><tt>BasicBlock</tt></a>
				620	</div>
				621
				622	<div class="doc_text">
				623
				624	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				625	easy to iterate over the individual instructions that make up
				626	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				627	a <tt>BasicBlock</tt>:</p>
				628
Chris Lattner	55c0461	2005-03-06 06:00:13 +0000	[diff] [blame]	629	<pre>
				630	// blk is a pointer to a BasicBlock instance
				631	for (BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
				632	// the next statement works since operator<<(ostream&,...)
				633	// is overloaded for Instruction&
				634	std::cerr << *i << "\n";
				635	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	636
				637	<p>However, this isn't really the best way to print out the contents of a
				638	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				639	anything you'll care about, you could have just invoked the print routine on the
Chris Lattner	55c0461	2005-03-06 06:00:13 +0000	[diff] [blame]	640	basic block itself: <tt>std::cerr << *blk << "\n";</tt>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	641
				642	</div>
				643
				644	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	645	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	646	<a name="iterate_institer">Iterating over the </a><a
				647	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				648	href="#Function"><tt>Function</tt></a>
				649	</div>
				650
				651	<div class="doc_text">
				652
				653	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				654	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				655	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				656	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				657	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]	658	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]	659
Chris Lattner	ac5bb69	2005-11-28 02:30:22 +0000	[diff] [blame]	660	<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> std::cerr << *i << "\n";<br></pre>
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	661	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				662	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	663	initialize a worklist to contain all instructions in a <tt>Function</tt>
				664	F, all you would need to do is something like:
				665	<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]	666
				667	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				668	<tt>Function</tt> pointed to by F.</p>
				669
				670	</div>
				671
				672	<!-- _______________________________________________________________________ -->
				673	<div class="doc_subsubsection">
				674	<a name="iterate_convert">Turning an iterator into a class pointer (and
				675	vice-versa)</a>
				676	</div>
				677
				678	<div class="doc_text">
				679
				680	<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]	681	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]	682	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	683	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]	684	is a <tt>BasicBlock::const_iterator</tt>:</p>
				685
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	686	<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]	687
				688	<p>However, the iterators you'll be working with in the LLVM framework are
				689	special: they will automatically convert to a ptr-to-instance type whenever they
				690	need to. Instead of dereferencing the iterator and then taking the address of
				691	the result, you can simply assign the iterator to the proper pointer type and
				692	you get the dereference and address-of operation as a result of the assignment
				693	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				694	the last line of the last example,</p>
				695
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	696	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	697
				698	<p>is semantically equivalent to</p>
				699
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	700	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	701
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	702	<p>It's also possible to turn a class pointer into the corresponding iterator,
				703	and this is a constant time operation (very efficient). The following code
				704	snippet illustrates use of the conversion constructors provided by LLVM
				705	iterators. By using these, you can explicitly grab the iterator of something
				706	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	707
Chris Lattner	ac5bb69	2005-11-28 02:30:22 +0000	[diff] [blame]	708	<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()) std::cerr << it << "\n";<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	709
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	710	</div>
				711
				712	<!--_______________________________________________________________________-->
				713	<div class="doc_subsubsection">
				714	<a name="iterate_complex">Finding call sites: a slightly more complex
				715	example</a>
				716	</div>
				717
				718	<div class="doc_text">
				719
				720	<p>Say that you're writing a FunctionPass and would like to count all the
				721	locations in the entire module (that is, across every <tt>Function</tt>) where a
				722	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				723	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]	724	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]	725	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				726	is what we want to do:</p>
				727
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	728	<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]	729
				730	<p>And the actual code is (remember, since we're writing a
				731	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				732	override the <tt>runOnFunction</tt> method...):</p>
				733
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	734	<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
				735	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				736	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]	737
				738	</div>
				739
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	740	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	741	<div class="doc_subsubsection">
				742	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				743	</div>
				744
				745	<div class="doc_text">
				746
				747	<p>You may have noticed that the previous example was a bit oversimplified in
				748	that it did not deal with call sites generated by 'invoke' instructions. In
				749	this, and in other situations, you may find that you want to treat
				750	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				751	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				752	less closely-related things. For these cases, LLVM provides a handy wrapper
				753	class called <a
Reid Spencer	05fe4b0	2006-03-14 05:39:39 +0000	[diff] [blame]	754	href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	755	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				756	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	757	<tt>InvokeInst</tt>s.</p>
				758
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	759	<p>This class has "value semantics": it should be passed by value, not by
				760	reference and it should not be dynamically allocated or deallocated using
				761	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				762	assignable and constructable, with costs equivalents to that of a bare pointer.
				763	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]	764
				765	</div>
				766
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	767	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	768	<div class="doc_subsubsection">
				769	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				770	</div>
				771
				772	<div class="doc_text">
				773
				774	<p>Frequently, we might have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	775	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				776	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				777	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				778	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				779	particular function <tt>foo</tt>. Finding all of the instructions that
				780	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				781	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	782
Chris Lattner	ac5bb69	2005-11-28 02:30:22 +0000	[diff] [blame]	783	<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> std::cerr << "F is used in instruction:\n";<br> std::cerr << *Inst << "\n";<br> }<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	784
				785	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	786	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]	787	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				788	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				789	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				790	all of the values that a particular instruction uses (that is, the operands of
				791	the particular <tt>Instruction</tt>):</p>
				792
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	793	<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]	794
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	795	<!--
				796	def-use chains ("finding all users of"): Value::use_begin/use_end
				797	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]	798	-->
				799
				800	</div>
				801
				802	<!-- ======================================================================= -->
				803	<div class="doc_subsection">
				804	<a name="simplechanges">Making simple changes</a>
				805	</div>
				806
				807	<div class="doc_text">
				808
				809	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	810	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	811	transformations, it's fairly common to manipulate the contents of basic
				812	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	813	and gives example code.</p>
				814
				815	</div>
				816
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	817	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	818	<div class="doc_subsubsection">
				819	<a name="schanges_creating">Creating and inserting new
				820	<tt>Instruction</tt>s</a>
				821	</div>
				822
				823	<div class="doc_text">
				824
				825	<p><i>Instantiating Instructions</i></p>
				826
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	827	<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]	828	constructor for the kind of instruction to instantiate and provide the necessary
				829	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				830	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				831
				832	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				833
				834	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				835	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				836	subclass is likely to have varying default parameters which change the semantics
				837	of the instruction, so refer to the <a
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	838	href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	839	Instruction</a> that you're interested in instantiating.</p>
				840
				841	<p><i>Naming values</i></p>
				842
				843	<p>It is very useful to name the values of instructions when you're able to, as
				844	this facilitates the debugging of your transformations. If you end up looking
				845	at generated LLVM machine code, you definitely want to have logical names
				846	associated with the results of instructions! By supplying a value for the
				847	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				848	associate a logical name with the result of the instruction's execution at
				849	runtime. For example, say that I'm writing a transformation that dynamically
				850	allocates space for an integer on the stack, and that integer is going to be
				851	used as some kind of index by some other code. To accomplish this, I place an
				852	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				853	<tt>Function</tt>, and I'm intending to use it within the same
				854	<tt>Function</tt>. I might do:</p>
				855
				856	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				857
				858	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				859	execution value, which is a pointer to an integer on the runtime stack.</p>
				860
				861	<p><i>Inserting instructions</i></p>
				862
				863	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				864	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				865
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	866	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	867	<li>Insertion into an explicit instruction list
				868
				869	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				870	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				871	before <tt>*pi</tt>, we do the following: </p>
				872
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	873	<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>
				874
				875	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				876	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				877	classes provide constructors which take a pointer to a
				878	<tt>BasicBlock</tt> to be appended to. For example code that
				879	looked like: </p>
				880
				881	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				882
				883	<p>becomes: </p>
				884
				885	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				886
				887	<p>which is much cleaner, especially if you are creating
				888	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	889
				890	<li>Insertion into an implicit instruction list
				891
				892	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				893	are implicitly associated with an existing instruction list: the instruction
				894	list of the enclosing basic block. Thus, we could have accomplished the same
				895	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				896	</p>
				897
				898	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				899
				900	<p>In fact, this sequence of steps occurs so frequently that the
				901	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				902	constructors which take (as a default parameter) a pointer to an
				903	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				904	precede. That is, <tt>Instruction</tt> constructors are capable of
				905	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				906	provided instruction, immediately before that instruction. Using an
				907	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				908	parameter, the above code becomes:</p>
				909
				910	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				911
				912	<p>which is much cleaner, especially if you're creating a lot of
				913	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				914	</ul>
				915
				916	</div>
				917
				918	<!--_______________________________________________________________________-->
				919	<div class="doc_subsubsection">
				920	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				921	</div>
				922
				923	<div class="doc_text">
				924
				925	<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]	926	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	927	you must have a pointer to the instruction that you wish to delete. Second, you
				928	need to obtain the pointer to that instruction's basic block. You use the
				929	pointer to the basic block to get its list of instructions and then use the
				930	erase function to remove your instruction. For example:</p>
				931
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	932	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				933	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]	934
				935	</div>
				936
				937	<!--_______________________________________________________________________-->
				938	<div class="doc_subsubsection">
				939	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				940	<tt>Value</tt></a>
				941	</div>
				942
				943	<div class="doc_text">
				944
				945	<p><i>Replacing individual instructions</i></p>
				946
				947	<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]	948	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	949	and <tt>ReplaceInstWithInst</tt>.</p>
				950
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	951	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	952
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	953	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	954	<li><tt>ReplaceInstWithValue</tt>
				955
				956	<p>This function replaces all uses (within a basic block) of a given
				957	instruction with a value, and then removes the original instruction. The
				958	following example illustrates the replacement of the result of a particular
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	959	<tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	960	pointer to an integer.</p>
				961
				962	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				963
				964	<li><tt>ReplaceInstWithInst</tt>
				965
				966	<p>This function replaces a particular instruction with another
				967	instruction. The following example illustrates the replacement of one
				968	<tt>AllocaInst</tt> with another.</p>
				969
				970	<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]	971	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	972
				973	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				974
				975	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				976	<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]	977	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				978	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]	979	information.</p>
				980
				981	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				982	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				983	ReplaceInstWithValue, ReplaceInstWithInst -->
				984
				985	</div>
				986
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	987	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	988	<div class="doc_section">
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	989	<a name="advanced">Advanced Topics</a>
				990	</div>
				991	<!-- *********************************************************************** -->
				992
				993	<div class="doc_text">
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	994	<p>
				995	This section describes some of the advanced or obscure API's that most clients
				996	do not need to be aware of. These API's tend manage the inner workings of the
				997	LLVM system, and only need to be accessed in unusual circumstances.
				998	</p>
				999	</div>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	1000
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1001	<!-- ======================================================================= -->
				1002	<div class="doc_subsection">
				1003	<a name="TypeResolve">LLVM Type Resolution</a>
				1004	</div>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	1005
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1006	<div class="doc_text">
				1007
				1008	<p>
				1009	The LLVM type system has a very simple goal: allow clients to compare types for
				1010	structural equality with a simple pointer comparison (aka a shallow compare).
				1011	This goal makes clients much simpler and faster, and is used throughout the LLVM
				1012	system.
				1013	</p>
				1014
				1015	<p>
				1016	Unfortunately achieving this goal is not a simple matter. In particular,
				1017	recursive types and late resolution of opaque types makes the situation very
				1018	difficult to handle. Fortunately, for the most part, our implementation makes
				1019	most clients able to be completely unaware of the nasty internal details. The
				1020	primary case where clients are exposed to the inner workings of it are when
				1021	building a recursive type. In addition to this case, the LLVM bytecode reader,
				1022	assembly parser, and linker also have to be aware of the inner workings of this
				1023	system.
				1024	</p>
				1025
Chris Lattner	0f876db	2005-04-25 15:47:57 +0000	[diff] [blame]	1026	<p>
				1027	For our purposes below, we need three concepts. First, an "Opaque Type" is
				1028	exactly as defined in the <a href="LangRef.html#t_opaque">language
				1029	reference</a>. Second an "Abstract Type" is any type which includes an
				1030	opaque type as part of its type graph (for example "<tt>{ opaque, int }</tt>").
				1031	Third, a concrete type is a type that is not an abstract type (e.g. "<tt>[ int,
				1032	float }</tt>").
				1033	</p>
				1034
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1035	</div>
				1036
				1037	<!-- ______________________________________________________________________ -->
				1038	<div class="doc_subsubsection">
				1039	<a name="BuildRecType">Basic Recursive Type Construction</a>
				1040	</div>
				1041
				1042	<div class="doc_text">
				1043
				1044	<p>
				1045	Because the most common question is "how do I build a recursive type with LLVM",
				1046	we answer it now and explain it as we go. Here we include enough to cause this
				1047	to be emitted to an output .ll file:
				1048	</p>
				1049
				1050	<pre>
				1051	%mylist = type { %mylist*, int }
				1052	</pre>
				1053
				1054	<p>
				1055	To build this, use the following LLVM APIs:
				1056	</p>
				1057
				1058	<pre>
				1059	//<i> Create the initial outer struct.</i>
				1060	<a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
				1061	std::vector<const Type*> Elts;
				1062	Elts.push_back(PointerType::get(StructTy));
				1063	Elts.push_back(Type::IntTy);
				1064	StructType *NewSTy = StructType::get(Elts);
				1065
				1066	//<i> At this point, NewSTy = "{ opaque*, int }". Tell VMCore that</i>
				1067	//<i> the struct and the opaque type are actually the same.</i>
				1068	cast<OpaqueType>(StructTy.get())-><a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
				1069
				1070	// <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
				1071	// <i>kept up-to-date.</i>
				1072	NewSTy = cast<StructType>(StructTy.get());
				1073
				1074	// <i>Add a name for the type to the module symbol table (optional).</i>
				1075	MyModule->addTypeName("mylist", NewSTy);
				1076	</pre>
				1077
				1078	<p>
				1079	This code shows the basic approach used to build recursive types: build a
				1080	non-recursive type using 'opaque', then use type unification to close the cycle.
				1081	The type unification step is performed by the <tt><a
				1082	ref="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
				1083	described next. After that, we describe the <a
				1084	href="#PATypeHolder">PATypeHolder class</a>.
				1085	</p>
				1086
				1087	</div>
				1088
				1089	<!-- ______________________________________________________________________ -->
				1090	<div class="doc_subsubsection">
				1091	<a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
				1092	</div>
				1093
				1094	<div class="doc_text">
				1095	<p>
				1096	The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
				1097	While this method is actually a member of the DerivedType class, it is most
				1098	often used on OpaqueType instances. Type unification is actually a recursive
				1099	process. After unification, types can become structurally isomorphic to
				1100	existing types, and all duplicates are deleted (to preserve pointer equality).
				1101	</p>
				1102
				1103	<p>
				1104	In the example above, the OpaqueType object is definitely deleted.
				1105	Additionally, if there is an "{ \2*, int}" type already created in the system,
				1106	the pointer and struct type created are <b>also</b> deleted. Obviously whenever
				1107	a type is deleted, any "Type*" pointers in the program are invalidated. As
				1108	such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
				1109	live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
				1110	types can never move or be deleted). To deal with this, the <a
				1111	href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
				1112	reference to a possibly refined type, and the <a
				1113	href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
				1114	complex datastructures.
				1115	</p>
				1116
				1117	</div>
				1118
				1119	<!-- ______________________________________________________________________ -->
				1120	<div class="doc_subsubsection">
				1121	<a name="PATypeHolder">The PATypeHolder Class</a>
				1122	</div>
				1123
				1124	<div class="doc_text">
				1125	<p>
				1126	PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
				1127	happily goes about nuking types that become isomorphic to existing types, it
				1128	automatically updates all PATypeHolder objects to point to the new type. In the
				1129	example above, this allows the code to maintain a pointer to the resultant
				1130	resolved recursive type, even though the Type*'s are potentially invalidated.
				1131	</p>
				1132
				1133	<p>
				1134	PATypeHolder is an extremely light-weight object that uses a lazy union-find
				1135	implementation to update pointers. For example the pointer from a Value to its
				1136	Type is maintained by PATypeHolder objects.
				1137	</p>
				1138
				1139	</div>
				1140
				1141	<!-- ______________________________________________________________________ -->
				1142	<div class="doc_subsubsection">
				1143	<a name="AbstractTypeUser">The AbstractTypeUser Class</a>
				1144	</div>
				1145
				1146	<div class="doc_text">
				1147
				1148	<p>
				1149	Some data structures need more to perform more complex updates when types get
				1150	resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
				1151	move and potentially merge type planes in its representation when a pointer
				1152	changes.</p>
				1153
				1154	<p>
				1155	To support this, a class can derive from the AbstractTypeUser class. This class
				1156	allows it to get callbacks when certain types are resolved. To register to get
				1157	callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
Chris Lattner	0f876db	2005-04-25 15:47:57 +0000	[diff] [blame]	1158	methods can be called on a type. Note that these methods only work for <i>
				1159	abstract</i> types. Concrete types (those that do not include an opaque objects
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1160	somewhere) can never be refined.
				1161	</p>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	1162	</div>
				1163
				1164
				1165	<!-- ======================================================================= -->
				1166	<div class="doc_subsection">
				1167	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1168	</div>
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1169
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	1170	<div class="doc_text">
				1171	<p>This class provides a symbol table that the <a
				1172	href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1173	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1174	provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
				1175	href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1176	type. It hides the data it contains and provides access to it through a
				1177	controlled interface.</p>
				1178
				1179	<p>Note that the symbol table class is should not be directly accessed by most
				1180	clients. It should only be used when iteration over the symbol table names
				1181	themselves are required, which is very special purpose. Note that not all LLVM
				1182	<a href="#Value">Value</a>s have names, and those without names (i.e. they have
				1183	an empty name) do not exist in the symbol table.
				1184	</p>
				1185
				1186	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1187	structure of the information it holds. The class contains two
				1188	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1189	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1190	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1191	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1192	however, are stored in a single dimension and accessed only by name.</p>
				1193
				1194	<p>The interface of this class provides three basic types of operations:
				1195	<ol>
				1196	<li><em>Accessors</em>. Accessors provide read-only access to information
				1197	such as finding a value for a name with the
				1198	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1199	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1200	<tt>SymbolTable</tt> with methods like
				1201	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1202	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1203	of the symbol table in well defined ways, such as the method
				1204	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1205	</ol>
				1206
				1207	<h3>Accessors</h3>
				1208	<dl>
				1209	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1210	</dt>
				1211	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1212	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1213	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1214
				1215	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1216	<dd>The <tt>lookupType</tt> method searches through the types for a
				1217	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1218	is not found, null is returned.</dd>
				1219
				1220	<dt><tt>bool hasTypes() const</tt>:</dt>
				1221	<dd>This function returns true if an entry has been made into the type
				1222	map.</dd>
				1223
				1224	<dt><tt>bool isEmpty() const</tt>:</dt>
				1225	<dd>This function returns true if both the value and types maps are
				1226	empty</dd>
				1227	</dl>
				1228
				1229	<h3>Mutators</h3>
				1230	<dl>
				1231	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1232	<dd>This method adds the provided value to the symbol table. The Value must
				1233	have both a name and a type which are extracted and used to place the value
				1234	in the correct type plane under the value's name.</dd>
				1235
				1236	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1237	<dd> Inserts a constant or type into the symbol table with the specified
				1238	name. There can be a many to one mapping between names and constants
				1239	or types.</dd>
				1240
				1241	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1242	<dd> Inserts a type into the symbol table with the specified name. There
				1243	can be a many-to-one mapping between names and types. This method
				1244	allows a type with an existing entry in the symbol table to get
				1245	a new name.</dd>
				1246
				1247	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1248	<dd> This method removes a named value from the symbol table. The
				1249	type and name of the Value are extracted from \p N and used to
				1250	lookup the Value in the correct type plane. If the Value is
				1251	not in the symbol table, this method silently ignores the
				1252	request.</dd>
				1253
				1254	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1255	<dd> This method removes a named type from the symbol table. The
				1256	name of the type is extracted from \P T and used to look up
				1257	the Type in the type map. If the Type is not in the symbol
				1258	table, this method silently ignores the request.</dd>
				1259
				1260	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1261	<dd> Remove a constant or type with the specified name from the
				1262	symbol table.</dd>
				1263
				1264	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1265	<dd> Remove a type with the specified name from the symbol table.
				1266	Returns the removed Type.</dd>
				1267
				1268	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1269	<dd> Removes a specific value from the symbol table.
				1270	Returns the removed value.</dd>
				1271
				1272	<dt><tt>bool strip()</tt>:</dt>
				1273	<dd> This method will strip the symbol table of its names leaving
				1274	the type and values. </dd>
				1275
				1276	<dt><tt>void clear()</tt>:</dt>
				1277	<dd>Empty the symbol table completely.</dd>
				1278	</dl>
				1279
				1280	<h3>Iteration</h3>
				1281	<p>The following functions describe three types of iterators you can obtain
				1282	the beginning or end of the sequence for both const and non-const. It is
				1283	important to keep track of the different kinds of iterators. There are
				1284	three idioms worth pointing out:</p>
				1285	<table>
				1286	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1287	<tr>
				1288	<td align="left">Planes Of name/Value maps</td><td>PI</td>
				1289	<td align="left"><pre><tt>
				1290	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
				1291	PE = ST.plane_end(); PI != PE; ++PI ) {
				1292	PI->first // This is the Type* of the plane
				1293	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1294	</tt></pre></td>
				1295	</tr>
				1296	<tr>
				1297	<td align="left">All name/Type Pairs</td><td>TI</td>
				1298	<td align="left"><pre><tt>
				1299	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1300	TE = ST.type_end(); TI != TE; ++TI )
				1301	TI->first // This is the name of the type
				1302	TI->second // This is the Type* value associated with the name
				1303	</tt></pre></td>
				1304	</tr>
				1305	<tr>
				1306	<td align="left">name/Value pairs in a plane</td><td>VI</td>
				1307	<td align="left"><pre><tt>
				1308	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1309	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1310	VI->first // This is the name of the Value
				1311	VI->second // This is the Value* value associated with the name
				1312	</tt></pre></td>
				1313	</tr>
				1314	</table>
				1315
				1316	<p>Using the recommended iterator names and idioms will help you avoid
				1317	making mistakes. Of particular note, make sure that whenever you use
				1318	value_begin(SomeType) that you always compare the resulting iterator
				1319	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1320	will loop infinitely.</p>
				1321
				1322	<dl>
				1323
				1324	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1325	<dd>Get an iterator that starts at the beginning of the type planes.
				1326	The iterator will iterate over the Type/ValueMap pairs in the
				1327	type planes. </dd>
				1328
				1329	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1330	<dd>Get a const_iterator that starts at the beginning of the type
				1331	planes. The iterator will iterate over the Type/ValueMap pairs
				1332	in the type planes. </dd>
				1333
				1334	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1335	<dd>Get an iterator at the end of the type planes. This serves as
				1336	the marker for end of iteration over the type planes.</dd>
				1337
				1338	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				1339	<dd>Get a const_iterator at the end of the type planes. This serves as
				1340	the marker for end of iteration over the type planes.</dd>
				1341
				1342	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1343	<dd>Get an iterator that starts at the beginning of a type plane.
				1344	The iterator will iterate over the name/value pairs in the type plane.
				1345	Note: The type plane must already exist before using this.</dd>
				1346
				1347	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				1348	<dd>Get a const_iterator that starts at the beginning of a type plane.
				1349	The iterator will iterate over the name/value pairs in the type plane.
				1350	Note: The type plane must already exist before using this.</dd>
				1351
				1352	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				1353	<dd>Get an iterator to the end of a type plane. This serves as the marker
				1354	for end of iteration of the type plane.
				1355	Note: The type plane must already exist before using this.</dd>
				1356
				1357	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				1358	<dd>Get a const_iterator to the end of a type plane. This serves as the
				1359	marker for end of iteration of the type plane.
				1360	Note: the type plane must already exist before using this.</dd>
				1361
				1362	<dt><tt>type_iterator type_begin()</tt>:</dt>
				1363	<dd>Get an iterator to the start of the name/Type map.</dd>
				1364
				1365	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				1366	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				1367
				1368	<dt><tt>type_iterator type_end()</tt>:</dt>
				1369	<dd>Get an iterator to the end of the name/Type map. This serves as the
				1370	marker for end of iteration of the types.</dd>
				1371
				1372	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				1373	<dd>Get a const-iterator to the end of the name/Type map. This serves
				1374	as the marker for end of iteration of the types.</dd>
				1375
				1376	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				1377	<dd>This method returns a plane_const_iterator for iteration over
				1378	the type planes starting at a specific plane, given by \p Ty.</dd>
				1379
				1380	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				1381	<dd>This method returns a plane_iterator for iteration over the
				1382	type planes starting at a specific plane, given by \p Ty.</dd>
				1383
				1384	</dl>
				1385	</div>
				1386
				1387
				1388
				1389	<!-- *********************************************************************** -->
				1390	<div class="doc_section">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1391	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				1392	</div>
				1393	<!-- *********************************************************************** -->
				1394
				1395	<div class="doc_text">
				1396
				1397	<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]	1398	being inspected or transformed. The core LLVM classes are defined in
				1399	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1400	the <tt>lib/VMCore</tt> directory.</p>
				1401
				1402	</div>
				1403
				1404	<!-- ======================================================================= -->
				1405	<div class="doc_subsection">
				1406	<a name="Value">The <tt>Value</tt> class</a>
				1407	</div>
				1408
				1409	<div>
				1410
				1411	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				1412	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1413	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]	1414
				1415	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				1416	base. It represents a typed value that may be used (among other things) as an
				1417	operand to an instruction. There are many different types of <tt>Value</tt>s,
				1418	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				1419	href="#Argument"><tt>Argument</tt></a>s. Even <a
				1420	href="#Instruction"><tt>Instruction</tt></a>s and <a
				1421	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				1422
				1423	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				1424	for a program. For example, an incoming argument to a function (represented
				1425	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				1426	every instruction in the function that references the argument. To keep track
				1427	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				1428	href="#User"><tt>User</tt></a>s that is using it (the <a
				1429	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				1430	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				1431	def-use information in the program, and is accessible through the <tt>use_</tt>*
				1432	methods, shown below.</p>
				1433
				1434	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				1435	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				1436	method. In addition, all LLVM values can be named. The "name" of the
				1437	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				1438
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1439	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1440
				1441	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				1442	that the name of any value may be missing (an empty string), so names should
				1443	<b>ONLY</b> be used for debugging (making the source code easier to read,
				1444	debugging printouts), they should not be used to keep track of values or map
				1445	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				1446	<tt>Value</tt> itself instead.</p>
				1447
				1448	<p>One important aspect of LLVM is that there is no distinction between an SSA
				1449	variable and the operation that produces it. Because of this, any reference to
				1450	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]	1451	argument, for example) is represented as a direct pointer to the instance of
				1452	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1453	represents this value. Although this may take some getting used to, it
				1454	simplifies the representation and makes it easier to manipulate.</p>
				1455
				1456	</div>
				1457
				1458	<!-- _______________________________________________________________________ -->
				1459	<div class="doc_subsubsection">
				1460	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				1461	</div>
				1462
				1463	<div class="doc_text">
				1464
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1465	<ul>
				1466	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1467	use-list<br>
				1468	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1469	the use-list<br>
				1470	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1471	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1472	<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]	1473	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1474	the use-list.<br>
				1475	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1476	use-list.<br>
				1477	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1478	element in the list.
				1479	<p> These methods are the interface to access the def-use
				1480	information in LLVM. As with all other iterators in LLVM, the naming
				1481	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]	1482	</li>
				1483	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1484	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1485	</li>
				1486	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1487	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1488	<tt>void setName(const std::string &Name)</tt>
				1489	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1490	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1491	</li>
				1492	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1493
				1494	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1495	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1496	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1497	produces a constant value (for example through constant folding), you can
				1498	replace all uses of the instruction with the constant like this:</p>
				1499
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1500	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1501	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1502
				1503	</div>
				1504
				1505	<!-- ======================================================================= -->
				1506	<div class="doc_subsection">
				1507	<a name="User">The <tt>User</tt> class</a>
				1508	</div>
				1509
				1510	<div class="doc_text">
				1511
				1512	<p>
				1513	<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]	1514	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]	1515	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1516
				1517	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1518	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1519	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1520	referring to. The <tt>User</tt> class itself is a subclass of
				1521	<tt>Value</tt>.</p>
				1522
				1523	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1524	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1525	Single Assignment (SSA) form, there can only be one definition referred to,
				1526	allowing this direct connection. This connection provides the use-def
				1527	information in LLVM.</p>
				1528
				1529	</div>
				1530
				1531	<!-- _______________________________________________________________________ -->
				1532	<div class="doc_subsubsection">
				1533	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1534	</div>
				1535
				1536	<div class="doc_text">
				1537
				1538	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1539	an index access interface and through an iterator based interface.</p>
				1540
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1541	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1542	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1543	<tt>unsigned getNumOperands()</tt>
				1544	<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]	1545	convenient form for direct access.</p></li>
				1546
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1547	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1548	list<br>
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	1549	<tt>op_iterator op_begin()</tt> - Get an iterator to the start of
				1550	the operand list.<br>
				1551	<tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1552	operand list.
				1553	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1554	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1555	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1556
				1557	</div>
				1558
				1559	<!-- ======================================================================= -->
				1560	<div class="doc_subsection">
				1561	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1562	</div>
				1563
				1564	<div class="doc_text">
				1565
				1566	<p><tt>#include "</tt><tt><a
				1567	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1568	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]	1569	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1570	href="#Value"><tt>Value</tt></a></p>
				1571
				1572	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1573	instructions. It provides only a few methods, but is a very commonly used
				1574	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1575	opcode (instruction type) and the parent <a
				1576	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1577	into. To represent a specific type of instruction, one of many subclasses of
				1578	<tt>Instruction</tt> are used.</p>
				1579
				1580	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1581	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1582	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1583	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1584	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1585	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1586	file contains some meta-data about the various different types of instructions
				1587	in LLVM. It describes the enum values that are used as opcodes (for example
				1588	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1589	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1590	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1591	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1592	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]	1593	<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1594
				1595	</div>
				1596
				1597	<!-- _______________________________________________________________________ -->
				1598	<div class="doc_subsubsection">
				1599	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1600	class</a>
				1601	</div>
				1602
				1603	<div class="doc_text">
				1604
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1605	<ul>
				1606	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1607	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1608	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1609	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1610	<p>Returns true if the instruction writes to memory, i.e. it is a
				1611	<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]	1612	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1613	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1614	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1615	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1616	in all ways to the original except that the instruction has no parent
				1617	(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]	1618	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1619	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1620
				1621	</div>
				1622
				1623	<!-- ======================================================================= -->
				1624	<div class="doc_subsection">
				1625	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1626	</div>
				1627
				1628	<div class="doc_text">
				1629
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1630	<p><tt>#include "<a
				1631	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1632	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1633	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1634	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1635
				1636	<p>This class represents a single entry multiple exit section of the code,
				1637	commonly known as a basic block by the compiler community. The
				1638	<tt>BasicBlock</tt> class maintains a list of <a
				1639	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1640	Matching the language definition, the last element of this list of instructions
				1641	is always a terminator instruction (a subclass of the <a
				1642	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1643
				1644	<p>In addition to tracking the list of instructions that make up the block, the
				1645	<tt>BasicBlock</tt> class also keeps track of the <a
				1646	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1647
				1648	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1649	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1650	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1651	<tt>label</tt>.</p>
				1652
				1653	</div>
				1654
				1655	<!-- _______________________________________________________________________ -->
				1656	<div class="doc_subsubsection">
				1657	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1658	class</a>
				1659	</div>
				1660
				1661	<div class="doc_text">
				1662
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1663	<ul>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1664
				1665	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1666	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1667
				1668	<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1669	insertion into a function. The constructor optionally takes a name for the new
				1670	block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
				1671	the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
				1672	automatically inserted at the end of the specified <a
				1673	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1674	manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
				1675
				1676	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1677	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1678	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	1679	<tt>size()</tt>, <tt>empty()</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1680	STL-style functions for accessing the instruction list.
				1681
				1682	<p>These methods and typedefs are forwarding functions that have the same
				1683	semantics as the standard library methods of the same names. These methods
				1684	expose the underlying instruction list of a basic block in a way that is easy to
				1685	manipulate. To get the full complement of container operations (including
				1686	operations to update the list), you must use the <tt>getInstList()</tt>
				1687	method.</p></li>
				1688
				1689	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1690
				1691	<p>This method is used to get access to the underlying container that actually
				1692	holds the Instructions. This method must be used when there isn't a forwarding
				1693	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1694	to perform. Because there are no forwarding functions for "updating"
				1695	operations, you need to use this if you want to update the contents of a
				1696	<tt>BasicBlock</tt>.</p></li>
				1697
				1698	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1699
				1700	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1701	embedded into, or a null pointer if it is homeless.</p></li>
				1702
				1703	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1704
				1705	<p> Returns a pointer to the terminator instruction that appears at the end of
				1706	the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1707	instruction in the block is not a terminator, then a null pointer is
				1708	returned.</p></li>
				1709
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1710	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1711
				1712	</div>
				1713
				1714	<!-- ======================================================================= -->
				1715	<div class="doc_subsection">
				1716	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1717	</div>
				1718
				1719	<div class="doc_text">
				1720
				1721	<p><tt>#include "<a
				1722	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1723	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1724	Class</a><br>
Reid Spencer	be5e85e	2006-04-14 14:11:48 +0000	[diff] [blame]	1725	Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
				1726	<a href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1727
				1728	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1729	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1730	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1731	Because they are visible at global scope, they are also subject to linking with
				1732	other globals defined in different translation units. To control the linking
				1733	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1734	<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]	1735	defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1736
				1737	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1738	<tt>static</tt> in C), it is not visible to code outside the current translation
				1739	unit, and does not participate in linking. If it has external linkage, it is
				1740	visible to external code, and does participate in linking. In addition to
				1741	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1742	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1743
				1744	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1745	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1746	global is always a pointer to its contents. It is important to remember this
				1747	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1748	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1749	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1750	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1751	the address of the first element of this array and the value of the
				1752	<tt>GlobalVariable</tt> are the same, they have different types. The
				1753	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1754	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1755	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1756	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1757	Language Reference Manual</a>.</p>
				1758
				1759	</div>
				1760
				1761	<!-- _______________________________________________________________________ -->
				1762	<div class="doc_subsubsection">
				1763	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1764	class</a>
				1765	</div>
				1766
				1767	<div class="doc_text">
				1768
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1769	<ul>
				1770	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1771	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1772	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1773	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1774	<p> </p>
				1775	</li>
				1776	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1777	<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]	1778	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1779	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1780
				1781	</div>
				1782
				1783	<!-- ======================================================================= -->
				1784	<div class="doc_subsection">
				1785	<a name="Function">The <tt>Function</tt> class</a>
				1786	</div>
				1787
				1788	<div class="doc_text">
				1789
				1790	<p><tt>#include "<a
				1791	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]	1792	info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencer	be5e85e	2006-04-14 14:11:48 +0000	[diff] [blame]	1793	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
				1794	<a href="#Constant"><tt>Constant</tt></a>,
				1795	<a href="#User"><tt>User</tt></a>,
				1796	<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1797
				1798	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1799	actually one of the more complex classes in the LLVM heirarchy because it must
				1800	keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencer	be5e85e	2006-04-14 14:11:48 +0000	[diff] [blame]	1801	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
				1802	<a href="#Argument"><tt>Argument</tt></a>s, and a
				1803	<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1804
				1805	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1806	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1807	ordering of the blocks in the function, which indicate how the code will be
				1808	layed out by the backend. Additionally, the first <a
				1809	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1810	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1811	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1812	nodes from a single <tt>Function</tt>. If the <a
				1813	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1814	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1815	function hasn't been linked in yet.</p>
				1816
				1817	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1818	<tt>Function</tt> class also keeps track of the list of formal <a
				1819	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1820	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1821	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1822	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1823
				1824	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1825	LLVM feature that is only used when you have to look up a value by name. Aside
				1826	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1827	internally to make sure that there are not conflicts between the names of <a
				1828	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1829	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1830	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1831
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1832	<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
				1833	and therefore also a <a href="#Constant">Constant</a>. The value of the function
				1834	is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1835	</div>
				1836
				1837	<!-- _______________________________________________________________________ -->
				1838	<div class="doc_subsubsection">
				1839	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1840	class</a>
				1841	</div>
				1842
				1843	<div class="doc_text">
				1844
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1845	<ul>
				1846	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1847	Ty, LinkageTypes Linkage, const std::string &N = "", Module Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1848
				1849	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1850	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]	1851	create and what type of linkage the function should have. The <a
				1852	href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1853	specifies the formal arguments and return value for the function. The same
				1854	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1855	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1856	in which the function is defined. If this argument is provided, the function
				1857	will automatically be inserted into that module's list of
				1858	functions.</p></li>
				1859
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1860	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1861
				1862	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1863	function is "external", it does not have a body, and thus must be resolved
				1864	by linking with a function defined in a different translation unit.</p></li>
				1865
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1866	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1867	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1868
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	1869	<tt>begin()</tt>, <tt>end()</tt>
				1870	<tt>size()</tt>, <tt>empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1871
				1872	<p>These are forwarding methods that make it easy to access the contents of
				1873	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1874	list.</p></li>
				1875
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1876	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1877
				1878	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1879	is necessary to use when you need to update the list or perform a complex
				1880	action that doesn't have a forwarding method.</p></li>
				1881
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	1882	<li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1883	iterator<br>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	1884	<tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1885
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	1886	<tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	1887	<tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1888
				1889	<p>These are forwarding methods that make it easy to access the contents of
				1890	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1891	list.</p></li>
				1892
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1893	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1894
				1895	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1896	necessary to use when you need to update the list or perform a complex
				1897	action that doesn't have a forwarding method.</p></li>
				1898
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1899	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1900
				1901	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1902	function. Because the entry block for the function is always the first
				1903	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1904
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1905	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1906	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1907
				1908	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1909	<tt>Function</tt> and returns the return type of the function, or the <a
				1910	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1911	function.</p></li>
				1912
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1913	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1914
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1915	<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]	1916	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1917	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1918
				1919	</div>
				1920
				1921	<!-- ======================================================================= -->
				1922	<div class="doc_subsection">
				1923	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1924	</div>
				1925
				1926	<div class="doc_text">
				1927
				1928	<p><tt>#include "<a
				1929	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1930	<br>
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1931	doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencer	be5e85e	2006-04-14 14:11:48 +0000	[diff] [blame]	1932	Class</a><br>
				1933	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
				1934	<a href="#Constant"><tt>Constant</tt></a>,
				1935	<a href="#User"><tt>User</tt></a>,
				1936	<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1937
				1938	<p>Global variables are represented with the (suprise suprise)
				1939	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1940	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1941	always referenced by their address (global values must live in memory, so their
Reid Spencer	be5e85e	2006-04-14 14:11:48 +0000	[diff] [blame]	1942	"name" refers to their constant address). See
				1943	<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
				1944	variables may have an initial value (which must be a
				1945	<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
				1946	they may be marked as "constant" themselves (indicating that their contents
				1947	never change at runtime).</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1948	</div>
				1949
				1950	<!-- _______________________________________________________________________ -->
				1951	<div class="doc_subsubsection">
				1952	<a name="m_GlobalVariable">Important Public Members of the
				1953	<tt>GlobalVariable</tt> class</a>
				1954	</div>
				1955
				1956	<div class="doc_text">
				1957
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1958	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1959	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1960	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1961	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1962
				1963	<p>Create a new global variable of the specified type. If
				1964	<tt>isConstant</tt> is true then the global variable will be marked as
				1965	unchanging for the program. The Linkage parameter specifies the type of
				1966	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1967	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1968	the resultant global variable will have internal linkage. AppendingLinkage
				1969	concatenates together all instances (in different translation units) of the
				1970	variable into a single variable but is only applicable to arrays.  See
				1971	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1972	further details on linkage types. Optionally an initializer, a name, and the
				1973	module to put the variable into may be specified for the global variable as
				1974	well.</p></li>
				1975
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1976	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1977
				1978	<p>Returns true if this is a global variable that is known not to
				1979	be modified at runtime.</p></li>
				1980
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1981	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1982
				1983	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1984
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1985	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1986
				1987	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1988	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1989	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1990
				1991	</div>
				1992
				1993	<!-- ======================================================================= -->
				1994	<div class="doc_subsection">
				1995	<a name="Module">The <tt>Module</tt> class</a>
				1996	</div>
				1997
				1998	<div class="doc_text">
				1999
				2000	<p><tt>#include "<a
				2001	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]	2002	<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2003
				2004	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				2005	programs. An LLVM module is effectively either a translation unit of the
				2006	original program or a combination of several translation units merged by the
				2007	linker. The <tt>Module</tt> class keeps track of a list of <a
				2008	href="#Function"><tt>Function</tt></a>s, a list of <a
				2009	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				2010	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				2011	helpful member functions that try to make common operations easy.</p>
				2012
				2013	</div>
				2014
				2015	<!-- _______________________________________________________________________ -->
				2016	<div class="doc_subsubsection">
				2017	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				2018	</div>
				2019
				2020	<div class="doc_text">
				2021
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2022	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2023	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2024	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2025
				2026	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				2027	provide a name for it (probably based on the name of the translation unit).</p>
				2028
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2029	<ul>
				2030	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	2031	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2032
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	2033	<tt>begin()</tt>, <tt>end()</tt>
				2034	<tt>size()</tt>, <tt>empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2035
				2036	<p>These are forwarding methods that make it easy to access the contents of
				2037	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				2038	list.</p></li>
				2039
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2040	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2041
				2042	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				2043	necessary to use when you need to update the list or perform a complex
				2044	action that doesn't have a forwarding method.</p>
				2045
				2046	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2047	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2048
				2049	<hr>
				2050
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2051	<ul>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	2052	<li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2053
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	2054	<tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2055
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	2056	<tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	2057	<tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2058
				2059	<p> These are forwarding methods that make it easy to access the contents of
				2060	a <tt>Module</tt> object's <a
				2061	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				2062
				2063	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				2064
				2065	<p>Returns the list of <a
				2066	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				2067	use when you need to update the list or perform a complex action that
				2068	doesn't have a forwarding method.</p>
				2069
				2070	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2071	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2072
				2073	<hr>
				2074
				2075	<ul>
				2076	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				2077
				2078	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				2079	for this <tt>Module</tt>.</p>
				2080
				2081	<p><!-- Convenience methods --></p></li>
				2082	</ul>
				2083
				2084	<hr>
				2085
				2086	<ul>
				2087	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				2088	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				2089
				2090	<p>Look up the specified function in the <tt>Module</tt> <a
				2091	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				2092	<tt>null</tt>.</p></li>
				2093
				2094	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				2095	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				2096
				2097	<p>Look up the specified function in the <tt>Module</tt> <a
				2098	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				2099	external declaration for the function and return it.</p></li>
				2100
				2101	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				2102
				2103	<p>If there is at least one entry in the <a
				2104	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				2105	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				2106	string.</p></li>
				2107
				2108	<li><tt>bool addTypeName(const std::string &Name, const <a
				2109	href="#Type">Type</a> *Ty)</tt>
				2110
				2111	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				2112	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				2113	name, true is returned and the <a
				2114	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				2115	</ul>
				2116
				2117	</div>
				2118
				2119	<!-- ======================================================================= -->
				2120	<div class="doc_subsection">
				2121	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				2122	</div>
				2123
				2124	<div class="doc_text">
				2125
				2126	<p>Constant represents a base class for different types of constants. It
				2127	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				2128	ConstantArray etc for representing the various types of Constants.</p>
				2129
				2130	</div>
				2131
				2132	<!-- _______________________________________________________________________ -->
				2133	<div class="doc_subsubsection">
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2134	<a name="m_Constant">Important Public Methods</a>
				2135	</div>
				2136	<div class="doc_text">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2137	</div>
				2138
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2139	<!-- _______________________________________________________________________ -->
				2140	<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2141	<div class="doc_text">
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2142	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2143	<li>ConstantSInt : This subclass of Constant represents a signed integer
				2144	constant.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2145	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2146	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				2147	this constant. </li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2148	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2149	</li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2150	<li>ConstantUInt : This class represents an unsigned integer.
				2151	<ul>
				2152	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
				2153	this constant. </li>
				2154	</ul>
				2155	</li>
				2156	<li>ConstantFP : This class represents a floating point constant.
				2157	<ul>
				2158	<li><tt>double getValue() const</tt>: Returns the underlying value of
				2159	this constant. </li>
				2160	</ul>
				2161	</li>
				2162	<li>ConstantBool : This represents a boolean constant.
				2163	<ul>
				2164	<li><tt>bool getValue() const</tt>: Returns the underlying value of this
				2165	constant. </li>
				2166	</ul>
				2167	</li>
				2168	<li>ConstantArray : This represents a constant array.
				2169	<ul>
				2170	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	2171	a vector of component constants that makeup this array. </li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2172	</ul>
				2173	</li>
				2174	<li>ConstantStruct : This represents a constant struct.
				2175	<ul>
				2176	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	2177	a vector of component constants that makeup this array. </li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2178	</ul>
				2179	</li>
				2180	<li>GlobalValue : This represents either a global variable or a function. In
				2181	either case, the value is a constant fixed address (after linking).
				2182	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2183	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2184	</div>
				2185
				2186	<!-- ======================================================================= -->
				2187	<div class="doc_subsection">
				2188	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				2189	</div>
				2190
				2191	<div class="doc_text">
				2192
				2193	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				2194	type (like int, short etc) in LLVM is an instance of Type Class. All other
				2195	types are instances of subclasses of type like FunctionType, ArrayType
				2196	etc. DerivedType is the interface for all such dervied types including
				2197	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				2198	be recursive (StructType). There exists exactly one instance of any type
				2199	structure at a time. This allows using pointer equality of Type *s for comparing
				2200	types.</p>
				2201
				2202	</div>
				2203
				2204	<!-- _______________________________________________________________________ -->
				2205	<div class="doc_subsubsection">
				2206	<a name="m_Value">Important Public Methods</a>
				2207	</div>
				2208
				2209	<div class="doc_text">
				2210
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2211	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2212
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2213	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				2214	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				2215	not true for Float and Double. </li>
				2216
				2217	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				2218	unsigned. This is not quite the complement of isSigned... nonnumeric types
				2219	return false as they do with isSigned. This returns true for UByteTy,
				2220	UShortTy, UIntTy, and ULongTy. </li>
				2221
Chris Lattner	4573f1b	2004-07-08 17:49:37 +0000	[diff] [blame]	2222	<li><tt>bool isInteger() const</tt>: Equivalent to isSigned() \|\| isUnsigned().</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2223
				2224	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				2225	type, which is either Bool type or one of the Integer types.</li>
				2226
				2227	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				2228	floating point types.</li>
				2229
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2230	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				2231	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]	2232	example, uint to int or one pointer type to another.</li>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	2233	</ul>
				2234	</div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2235
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	2236	<!-- _______________________________________________________________________ -->
				2237	<div class="doc_subsubsection">
				2238	<a name="m_Value">Important Derived Types</a>
				2239	</div>
				2240	<div class="doc_text">
				2241	<ul>
				2242	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2243	<ul>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	2244	<li><tt>const Type * getElementType() const</tt>: Returns the type of each
				2245	of the elements in the sequential type. </li>
				2246	</ul>
				2247	</li>
				2248	<li>ArrayType : This is a subclass of SequentialType and defines interface for
				2249	array types.
				2250	<ul>
				2251	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				2252	elements in the array. </li>
				2253	</ul>
				2254	</li>
				2255	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				2256	<li>StructType : subclass of DerivedTypes for struct types </li>
				2257	<li>FunctionType : subclass of DerivedTypes for function types.
				2258	<ul>
				2259	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				2260	function</li>
				2261	<li><tt> const Type * getReturnType() const</tt>: Returns the
				2262	return type of the function.</li>
				2263	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
				2264	the type of the ith parameter.</li>
				2265	<li><tt> const unsigned getNumParams() const</tt>: Returns the
				2266	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2267	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2268	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2269	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2270	</div>
				2271
				2272	<!-- ======================================================================= -->
				2273	<div class="doc_subsection">
				2274	<a name="Argument">The <tt>Argument</tt> class</a>
				2275	</div>
				2276
				2277	<div class="doc_text">
				2278
				2279	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	2280	arguments to a function. A Function maintains a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2281	arguments. An argument has a pointer to the parent Function.</p>
				2282
				2283	</div>
				2284
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2285	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2286	<hr>
				2287	<address>
				2288	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2289	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2290	<a href="http://validator.w3.org/check/referer"><img
				2291	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2292
				2293	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2294	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
Reid Spencer	05fe4b0	2006-03-14 05:39:39 +0000	[diff] [blame]	2295	<a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2296	Last modified: $Date$
				2297	</address>
				2298
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2299	</body>
				2300	</html>