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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
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,
				519	you can usually use something like "<tt>call DAG.viewGraph()</tt>" to pop
				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
				532	</div>
				533
				534
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	535	<!-- *********************************************************************** -->
				536	<div class="doc_section">
				537	<a name="common">Helpful Hints for Common Operations</a>
				538	</div>
				539	<!-- *********************************************************************** -->
				540
				541	<div class="doc_text">
				542
				543	<p>This section describes how to perform some very simple transformations of
				544	LLVM code. This is meant to give examples of common idioms used, showing the
				545	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				546	you should also read about the main classes that you will be working with. The
				547	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				548	and descriptions of the main classes that you should know about.</p>
				549
				550	</div>
				551
				552	<!-- NOTE: this section should be heavy on example code -->
				553	<!-- ======================================================================= -->
				554	<div class="doc_subsection">
				555	<a name="inspection">Basic Inspection and Traversal Routines</a>
				556	</div>
				557
				558	<div class="doc_text">
				559
				560	<p>The LLVM compiler infrastructure have many different data structures that may
				561	be traversed. Following the example of the C++ standard template library, the
				562	techniques used to traverse these various data structures are all basically the
				563	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				564	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				565	function returns an iterator pointing to one past the last valid element of the
				566	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				567	between the two operations.</p>
				568
				569	<p>Because the pattern for iteration is common across many different aspects of
				570	the program representation, the standard template library algorithms may be used
				571	on them, and it is easier to remember how to iterate. First we show a few common
				572	examples of the data structures that need to be traversed. Other data
				573	structures are traversed in very similar ways.</p>
				574
				575	</div>
				576
				577	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	578	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	579	<a name="iterate_function">Iterating over the </a><a
				580	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				581	href="#Function"><tt>Function</tt></a>
				582	</div>
				583
				584	<div class="doc_text">
				585
				586	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				587	transform in some way; in particular, you'd like to manipulate its
				588	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				589	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				590	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				591	<tt>Instruction</tt>s it contains:</p>
				592
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	593	<pre> // func is a pointer to a Function instance<br> for (Function::iterator i = func->begin(), e = func->end(); i != e; ++i) {<br><br> // print out the name of the basic block if it has one, and then the<br> // number of instructions that it contains<br><br> cerr << "Basic block (name=" << i->getName() << ") has " <br> << i->size() << " instructions.\n";<br> }<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	594
				595	<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]	596	invoking member functions of the <tt>Instruction</tt> class. This is
				597	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	598	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	599	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				600
				601	</div>
				602
				603	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	604	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	605	<a name="iterate_basicblock">Iterating over the </a><a
				606	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				607	href="#BasicBlock"><tt>BasicBlock</tt></a>
				608	</div>
				609
				610	<div class="doc_text">
				611
				612	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				613	easy to iterate over the individual instructions that make up
				614	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				615	a <tt>BasicBlock</tt>:</p>
				616
Chris Lattner	55c0461	2005-03-06 06:00:13 +0000	[diff] [blame]	617	<pre>
				618	// blk is a pointer to a BasicBlock instance
				619	for (BasicBlock::iterator i = blk->begin(), e = blk->end(); i != e; ++i)
				620	// the next statement works since operator<<(ostream&,...)
				621	// is overloaded for Instruction&
				622	std::cerr << *i << "\n";
				623	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	624
				625	<p>However, this isn't really the best way to print out the contents of a
				626	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				627	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]	628	basic block itself: <tt>std::cerr << *blk << "\n";</tt>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	629
				630	</div>
				631
				632	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	633	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	634	<a name="iterate_institer">Iterating over the </a><a
				635	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				636	href="#Function"><tt>Function</tt></a>
				637	</div>
				638
				639	<div class="doc_text">
				640
				641	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				642	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				643	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				644	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				645	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]	646	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]	647
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	648	<pre>#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"<br>...<br>// Suppose F is a ptr to a function<br>for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)<br> cerr << *i << "\n";<br></pre>
Joel Stanley	e7be650	2002-09-09 15:50:33 +0000	[diff] [blame]	649	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				650	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	651	initialize a worklist to contain all instructions in a <tt>Function</tt>
				652	F, all you would need to do is something like:
				653	<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]	654
				655	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				656	<tt>Function</tt> pointed to by F.</p>
				657
				658	</div>
				659
				660	<!-- _______________________________________________________________________ -->
				661	<div class="doc_subsubsection">
				662	<a name="iterate_convert">Turning an iterator into a class pointer (and
				663	vice-versa)</a>
				664	</div>
				665
				666	<div class="doc_text">
				667
				668	<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]	669	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]	670	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	671	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]	672	is a <tt>BasicBlock::const_iterator</tt>:</p>
				673
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	674	<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]	675
				676	<p>However, the iterators you'll be working with in the LLVM framework are
				677	special: they will automatically convert to a ptr-to-instance type whenever they
				678	need to. Instead of dereferencing the iterator and then taking the address of
				679	the result, you can simply assign the iterator to the proper pointer type and
				680	you get the dereference and address-of operation as a result of the assignment
				681	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				682	the last line of the last example,</p>
				683
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	684	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	685
				686	<p>is semantically equivalent to</p>
				687
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	688	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	689
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	690	<p>It's also possible to turn a class pointer into the corresponding iterator,
				691	and this is a constant time operation (very efficient). The following code
				692	snippet illustrates use of the conversion constructors provided by LLVM
				693	iterators. By using these, you can explicitly grab the iterator of something
				694	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	695
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	696	<pre>void printNextInstruction(Instruction* inst) {<br> BasicBlock::iterator it(inst);<br> ++it; // after this line, it refers to the instruction after inst.<br> if (it != inst->getParent()->end()) cerr << it << "\n";<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	697
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	698	</div>
				699
				700	<!--_______________________________________________________________________-->
				701	<div class="doc_subsubsection">
				702	<a name="iterate_complex">Finding call sites: a slightly more complex
				703	example</a>
				704	</div>
				705
				706	<div class="doc_text">
				707
				708	<p>Say that you're writing a FunctionPass and would like to count all the
				709	locations in the entire module (that is, across every <tt>Function</tt>) where a
				710	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				711	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]	712	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]	713	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				714	is what we want to do:</p>
				715
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	716	<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]	717
				718	<p>And the actual code is (remember, since we're writing a
				719	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				720	override the <tt>runOnFunction</tt> method...):</p>
				721
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	722	<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
				723	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				724	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]	725
				726	</div>
				727
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	728	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	729	<div class="doc_subsubsection">
				730	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				731	</div>
				732
				733	<div class="doc_text">
				734
				735	<p>You may have noticed that the previous example was a bit oversimplified in
				736	that it did not deal with call sites generated by 'invoke' instructions. In
				737	this, and in other situations, you may find that you want to treat
				738	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				739	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				740	less closely-related things. For these cases, LLVM provides a handy wrapper
				741	class called <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	742	href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	743	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				744	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	745	<tt>InvokeInst</tt>s.</p>
				746
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	747	<p>This class has "value semantics": it should be passed by value, not by
				748	reference and it should not be dynamically allocated or deallocated using
				749	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				750	assignable and constructable, with costs equivalents to that of a bare pointer.
				751	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]	752
				753	</div>
				754
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	755	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	756	<div class="doc_subsubsection">
				757	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				758	</div>
				759
				760	<div class="doc_text">
				761
				762	<p>Frequently, we might have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	763	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				764	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				765	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				766	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				767	particular function <tt>foo</tt>. Finding all of the instructions that
				768	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				769	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	770
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	771	<pre>Function* F = ...;<br><br>for (Value::use_iterator i = F->use_begin(), e = F->use_end(); i != e; ++i) {<br> if (Instruction Inst = dyn_cast<Instruction>(i)) {<br> cerr << "F is used in instruction:\n";<br> cerr << *Inst << "\n";<br> }<br>}<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	772
				773	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	774	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]	775	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				776	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				777	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				778	all of the values that a particular instruction uses (that is, the operands of
				779	the particular <tt>Instruction</tt>):</p>
				780
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	781	<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]	782
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	783	<!--
				784	def-use chains ("finding all users of"): Value::use_begin/use_end
				785	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]	786	-->
				787
				788	</div>
				789
				790	<!-- ======================================================================= -->
				791	<div class="doc_subsection">
				792	<a name="simplechanges">Making simple changes</a>
				793	</div>
				794
				795	<div class="doc_text">
				796
				797	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	798	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	799	transformations, it's fairly common to manipulate the contents of basic
				800	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	801	and gives example code.</p>
				802
				803	</div>
				804
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	805	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	806	<div class="doc_subsubsection">
				807	<a name="schanges_creating">Creating and inserting new
				808	<tt>Instruction</tt>s</a>
				809	</div>
				810
				811	<div class="doc_text">
				812
				813	<p><i>Instantiating Instructions</i></p>
				814
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	815	<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]	816	constructor for the kind of instruction to instantiate and provide the necessary
				817	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				818	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				819
				820	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				821
				822	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				823	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				824	subclass is likely to have varying default parameters which change the semantics
				825	of the instruction, so refer to the <a
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	826	href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	827	Instruction</a> that you're interested in instantiating.</p>
				828
				829	<p><i>Naming values</i></p>
				830
				831	<p>It is very useful to name the values of instructions when you're able to, as
				832	this facilitates the debugging of your transformations. If you end up looking
				833	at generated LLVM machine code, you definitely want to have logical names
				834	associated with the results of instructions! By supplying a value for the
				835	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				836	associate a logical name with the result of the instruction's execution at
				837	runtime. For example, say that I'm writing a transformation that dynamically
				838	allocates space for an integer on the stack, and that integer is going to be
				839	used as some kind of index by some other code. To accomplish this, I place an
				840	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				841	<tt>Function</tt>, and I'm intending to use it within the same
				842	<tt>Function</tt>. I might do:</p>
				843
				844	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				845
				846	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				847	execution value, which is a pointer to an integer on the runtime stack.</p>
				848
				849	<p><i>Inserting instructions</i></p>
				850
				851	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				852	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				853
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	854	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	855	<li>Insertion into an explicit instruction list
				856
				857	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				858	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				859	before <tt>*pi</tt>, we do the following: </p>
				860
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	861	<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>
				862
				863	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				864	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				865	classes provide constructors which take a pointer to a
				866	<tt>BasicBlock</tt> to be appended to. For example code that
				867	looked like: </p>
				868
				869	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				870
				871	<p>becomes: </p>
				872
				873	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				874
				875	<p>which is much cleaner, especially if you are creating
				876	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	877
				878	<li>Insertion into an implicit instruction list
				879
				880	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				881	are implicitly associated with an existing instruction list: the instruction
				882	list of the enclosing basic block. Thus, we could have accomplished the same
				883	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				884	</p>
				885
				886	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				887
				888	<p>In fact, this sequence of steps occurs so frequently that the
				889	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				890	constructors which take (as a default parameter) a pointer to an
				891	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				892	precede. That is, <tt>Instruction</tt> constructors are capable of
				893	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				894	provided instruction, immediately before that instruction. Using an
				895	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				896	parameter, the above code becomes:</p>
				897
				898	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				899
				900	<p>which is much cleaner, especially if you're creating a lot of
				901	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				902	</ul>
				903
				904	</div>
				905
				906	<!--_______________________________________________________________________-->
				907	<div class="doc_subsubsection">
				908	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				909	</div>
				910
				911	<div class="doc_text">
				912
				913	<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]	914	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	915	you must have a pointer to the instruction that you wish to delete. Second, you
				916	need to obtain the pointer to that instruction's basic block. You use the
				917	pointer to the basic block to get its list of instructions and then use the
				918	erase function to remove your instruction. For example:</p>
				919
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	920	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				921	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]	922
				923	</div>
				924
				925	<!--_______________________________________________________________________-->
				926	<div class="doc_subsubsection">
				927	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				928	<tt>Value</tt></a>
				929	</div>
				930
				931	<div class="doc_text">
				932
				933	<p><i>Replacing individual instructions</i></p>
				934
				935	<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]	936	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	937	and <tt>ReplaceInstWithInst</tt>.</p>
				938
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	939	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	940
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	941	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	942	<li><tt>ReplaceInstWithValue</tt>
				943
				944	<p>This function replaces all uses (within a basic block) of a given
				945	instruction with a value, and then removes the original instruction. The
				946	following example illustrates the replacement of the result of a particular
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	947	<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]	948	pointer to an integer.</p>
				949
				950	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				951
				952	<li><tt>ReplaceInstWithInst</tt>
				953
				954	<p>This function replaces a particular instruction with another
				955	instruction. The following example illustrates the replacement of one
				956	<tt>AllocaInst</tt> with another.</p>
				957
				958	<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]	959	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	960
				961	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				962
				963	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				964	<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]	965	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				966	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]	967	information.</p>
				968
				969	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				970	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				971	ReplaceInstWithValue, ReplaceInstWithInst -->
				972
				973	</div>
				974
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	975	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	976	<div class="doc_section">
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	977	<a name="advanced">Advanced Topics</a>
				978	</div>
				979	<!-- *********************************************************************** -->
				980
				981	<div class="doc_text">
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	982	<p>
				983	This section describes some of the advanced or obscure API's that most clients
				984	do not need to be aware of. These API's tend manage the inner workings of the
				985	LLVM system, and only need to be accessed in unusual circumstances.
				986	</p>
				987	</div>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	988
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	989	<!-- ======================================================================= -->
				990	<div class="doc_subsection">
				991	<a name="TypeResolve">LLVM Type Resolution</a>
				992	</div>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	993
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	994	<div class="doc_text">
				995
				996	<p>
				997	The LLVM type system has a very simple goal: allow clients to compare types for
				998	structural equality with a simple pointer comparison (aka a shallow compare).
				999	This goal makes clients much simpler and faster, and is used throughout the LLVM
				1000	system.
				1001	</p>
				1002
				1003	<p>
				1004	Unfortunately achieving this goal is not a simple matter. In particular,
				1005	recursive types and late resolution of opaque types makes the situation very
				1006	difficult to handle. Fortunately, for the most part, our implementation makes
				1007	most clients able to be completely unaware of the nasty internal details. The
				1008	primary case where clients are exposed to the inner workings of it are when
				1009	building a recursive type. In addition to this case, the LLVM bytecode reader,
				1010	assembly parser, and linker also have to be aware of the inner workings of this
				1011	system.
				1012	</p>
				1013
Chris Lattner	0f876db	2005-04-25 15:47:57 +0000	[diff] [blame]	1014	<p>
				1015	For our purposes below, we need three concepts. First, an "Opaque Type" is
				1016	exactly as defined in the <a href="LangRef.html#t_opaque">language
				1017	reference</a>. Second an "Abstract Type" is any type which includes an
				1018	opaque type as part of its type graph (for example "<tt>{ opaque, int }</tt>").
				1019	Third, a concrete type is a type that is not an abstract type (e.g. "<tt>[ int,
				1020	float }</tt>").
				1021	</p>
				1022
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1023	</div>
				1024
				1025	<!-- ______________________________________________________________________ -->
				1026	<div class="doc_subsubsection">
				1027	<a name="BuildRecType">Basic Recursive Type Construction</a>
				1028	</div>
				1029
				1030	<div class="doc_text">
				1031
				1032	<p>
				1033	Because the most common question is "how do I build a recursive type with LLVM",
				1034	we answer it now and explain it as we go. Here we include enough to cause this
				1035	to be emitted to an output .ll file:
				1036	</p>
				1037
				1038	<pre>
				1039	%mylist = type { %mylist*, int }
				1040	</pre>
				1041
				1042	<p>
				1043	To build this, use the following LLVM APIs:
				1044	</p>
				1045
				1046	<pre>
				1047	//<i> Create the initial outer struct.</i>
				1048	<a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
				1049	std::vector<const Type*> Elts;
				1050	Elts.push_back(PointerType::get(StructTy));
				1051	Elts.push_back(Type::IntTy);
				1052	StructType *NewSTy = StructType::get(Elts);
				1053
				1054	//<i> At this point, NewSTy = "{ opaque*, int }". Tell VMCore that</i>
				1055	//<i> the struct and the opaque type are actually the same.</i>
				1056	cast<OpaqueType>(StructTy.get())-><a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
				1057
				1058	// <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
				1059	// <i>kept up-to-date.</i>
				1060	NewSTy = cast<StructType>(StructTy.get());
				1061
				1062	// <i>Add a name for the type to the module symbol table (optional).</i>
				1063	MyModule->addTypeName("mylist", NewSTy);
				1064	</pre>
				1065
				1066	<p>
				1067	This code shows the basic approach used to build recursive types: build a
				1068	non-recursive type using 'opaque', then use type unification to close the cycle.
				1069	The type unification step is performed by the <tt><a
				1070	ref="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
				1071	described next. After that, we describe the <a
				1072	href="#PATypeHolder">PATypeHolder class</a>.
				1073	</p>
				1074
				1075	</div>
				1076
				1077	<!-- ______________________________________________________________________ -->
				1078	<div class="doc_subsubsection">
				1079	<a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
				1080	</div>
				1081
				1082	<div class="doc_text">
				1083	<p>
				1084	The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
				1085	While this method is actually a member of the DerivedType class, it is most
				1086	often used on OpaqueType instances. Type unification is actually a recursive
				1087	process. After unification, types can become structurally isomorphic to
				1088	existing types, and all duplicates are deleted (to preserve pointer equality).
				1089	</p>
				1090
				1091	<p>
				1092	In the example above, the OpaqueType object is definitely deleted.
				1093	Additionally, if there is an "{ \2*, int}" type already created in the system,
				1094	the pointer and struct type created are <b>also</b> deleted. Obviously whenever
				1095	a type is deleted, any "Type*" pointers in the program are invalidated. As
				1096	such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
				1097	live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
				1098	types can never move or be deleted). To deal with this, the <a
				1099	href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
				1100	reference to a possibly refined type, and the <a
				1101	href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
				1102	complex datastructures.
				1103	</p>
				1104
				1105	</div>
				1106
				1107	<!-- ______________________________________________________________________ -->
				1108	<div class="doc_subsubsection">
				1109	<a name="PATypeHolder">The PATypeHolder Class</a>
				1110	</div>
				1111
				1112	<div class="doc_text">
				1113	<p>
				1114	PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
				1115	happily goes about nuking types that become isomorphic to existing types, it
				1116	automatically updates all PATypeHolder objects to point to the new type. In the
				1117	example above, this allows the code to maintain a pointer to the resultant
				1118	resolved recursive type, even though the Type*'s are potentially invalidated.
				1119	</p>
				1120
				1121	<p>
				1122	PATypeHolder is an extremely light-weight object that uses a lazy union-find
				1123	implementation to update pointers. For example the pointer from a Value to its
				1124	Type is maintained by PATypeHolder objects.
				1125	</p>
				1126
				1127	</div>
				1128
				1129	<!-- ______________________________________________________________________ -->
				1130	<div class="doc_subsubsection">
				1131	<a name="AbstractTypeUser">The AbstractTypeUser Class</a>
				1132	</div>
				1133
				1134	<div class="doc_text">
				1135
				1136	<p>
				1137	Some data structures need more to perform more complex updates when types get
				1138	resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
				1139	move and potentially merge type planes in its representation when a pointer
				1140	changes.</p>
				1141
				1142	<p>
				1143	To support this, a class can derive from the AbstractTypeUser class. This class
				1144	allows it to get callbacks when certain types are resolved. To register to get
				1145	callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
Chris Lattner	0f876db	2005-04-25 15:47:57 +0000	[diff] [blame]	1146	methods can be called on a type. Note that these methods only work for <i>
				1147	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]	1148	somewhere) can never be refined.
				1149	</p>
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	1150	</div>
				1151
				1152
				1153	<!-- ======================================================================= -->
				1154	<div class="doc_subsection">
				1155	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1156	</div>
Chris Lattner	f1b200b	2005-04-23 17:27:36 +0000	[diff] [blame]	1157
Chris Lattner	d9d6e10	2005-04-23 16:10:52 +0000	[diff] [blame]	1158	<div class="doc_text">
				1159	<p>This class provides a symbol table that the <a
				1160	href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1161	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1162	provide a name for any <a href="#Value"><tt>Value</tt></a> or <a
				1163	href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1164	type. It hides the data it contains and provides access to it through a
				1165	controlled interface.</p>
				1166
				1167	<p>Note that the symbol table class is should not be directly accessed by most
				1168	clients. It should only be used when iteration over the symbol table names
				1169	themselves are required, which is very special purpose. Note that not all LLVM
				1170	<a href="#Value">Value</a>s have names, and those without names (i.e. they have
				1171	an empty name) do not exist in the symbol table.
				1172	</p>
				1173
				1174	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1175	structure of the information it holds. The class contains two
				1176	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1177	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1178	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1179	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1180	however, are stored in a single dimension and accessed only by name.</p>
				1181
				1182	<p>The interface of this class provides three basic types of operations:
				1183	<ol>
				1184	<li><em>Accessors</em>. Accessors provide read-only access to information
				1185	such as finding a value for a name with the
				1186	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1187	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1188	<tt>SymbolTable</tt> with methods like
				1189	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1190	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1191	of the symbol table in well defined ways, such as the method
				1192	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1193	</ol>
				1194
				1195	<h3>Accessors</h3>
				1196	<dl>
				1197	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1198	</dt>
				1199	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1200	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1201	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1202
				1203	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1204	<dd>The <tt>lookupType</tt> method searches through the types for a
				1205	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1206	is not found, null is returned.</dd>
				1207
				1208	<dt><tt>bool hasTypes() const</tt>:</dt>
				1209	<dd>This function returns true if an entry has been made into the type
				1210	map.</dd>
				1211
				1212	<dt><tt>bool isEmpty() const</tt>:</dt>
				1213	<dd>This function returns true if both the value and types maps are
				1214	empty</dd>
				1215	</dl>
				1216
				1217	<h3>Mutators</h3>
				1218	<dl>
				1219	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1220	<dd>This method adds the provided value to the symbol table. The Value must
				1221	have both a name and a type which are extracted and used to place the value
				1222	in the correct type plane under the value's name.</dd>
				1223
				1224	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1225	<dd> Inserts a constant or type into the symbol table with the specified
				1226	name. There can be a many to one mapping between names and constants
				1227	or types.</dd>
				1228
				1229	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1230	<dd> Inserts a type into the symbol table with the specified name. There
				1231	can be a many-to-one mapping between names and types. This method
				1232	allows a type with an existing entry in the symbol table to get
				1233	a new name.</dd>
				1234
				1235	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1236	<dd> This method removes a named value from the symbol table. The
				1237	type and name of the Value are extracted from \p N and used to
				1238	lookup the Value in the correct type plane. If the Value is
				1239	not in the symbol table, this method silently ignores the
				1240	request.</dd>
				1241
				1242	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1243	<dd> This method removes a named type from the symbol table. The
				1244	name of the type is extracted from \P T and used to look up
				1245	the Type in the type map. If the Type is not in the symbol
				1246	table, this method silently ignores the request.</dd>
				1247
				1248	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1249	<dd> Remove a constant or type with the specified name from the
				1250	symbol table.</dd>
				1251
				1252	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1253	<dd> Remove a type with the specified name from the symbol table.
				1254	Returns the removed Type.</dd>
				1255
				1256	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1257	<dd> Removes a specific value from the symbol table.
				1258	Returns the removed value.</dd>
				1259
				1260	<dt><tt>bool strip()</tt>:</dt>
				1261	<dd> This method will strip the symbol table of its names leaving
				1262	the type and values. </dd>
				1263
				1264	<dt><tt>void clear()</tt>:</dt>
				1265	<dd>Empty the symbol table completely.</dd>
				1266	</dl>
				1267
				1268	<h3>Iteration</h3>
				1269	<p>The following functions describe three types of iterators you can obtain
				1270	the beginning or end of the sequence for both const and non-const. It is
				1271	important to keep track of the different kinds of iterators. There are
				1272	three idioms worth pointing out:</p>
				1273	<table>
				1274	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1275	<tr>
				1276	<td align="left">Planes Of name/Value maps</td><td>PI</td>
				1277	<td align="left"><pre><tt>
				1278	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
				1279	PE = ST.plane_end(); PI != PE; ++PI ) {
				1280	PI->first // This is the Type* of the plane
				1281	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1282	</tt></pre></td>
				1283	</tr>
				1284	<tr>
				1285	<td align="left">All name/Type Pairs</td><td>TI</td>
				1286	<td align="left"><pre><tt>
				1287	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1288	TE = ST.type_end(); TI != TE; ++TI )
				1289	TI->first // This is the name of the type
				1290	TI->second // This is the Type* value associated with the name
				1291	</tt></pre></td>
				1292	</tr>
				1293	<tr>
				1294	<td align="left">name/Value pairs in a plane</td><td>VI</td>
				1295	<td align="left"><pre><tt>
				1296	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1297	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1298	VI->first // This is the name of the Value
				1299	VI->second // This is the Value* value associated with the name
				1300	</tt></pre></td>
				1301	</tr>
				1302	</table>
				1303
				1304	<p>Using the recommended iterator names and idioms will help you avoid
				1305	making mistakes. Of particular note, make sure that whenever you use
				1306	value_begin(SomeType) that you always compare the resulting iterator
				1307	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1308	will loop infinitely.</p>
				1309
				1310	<dl>
				1311
				1312	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1313	<dd>Get an iterator that starts at the beginning of the type planes.
				1314	The iterator will iterate over the Type/ValueMap pairs in the
				1315	type planes. </dd>
				1316
				1317	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1318	<dd>Get a const_iterator that starts at the beginning of the type
				1319	planes. The iterator will iterate over the Type/ValueMap pairs
				1320	in the type planes. </dd>
				1321
				1322	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1323	<dd>Get an iterator at the end of the type planes. This serves as
				1324	the marker for end of iteration over the type planes.</dd>
				1325
				1326	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				1327	<dd>Get a const_iterator at the end of the type planes. This serves as
				1328	the marker for end of iteration over the type planes.</dd>
				1329
				1330	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1331	<dd>Get an iterator that starts at the beginning of a type plane.
				1332	The iterator will iterate over the name/value pairs in the type plane.
				1333	Note: The type plane must already exist before using this.</dd>
				1334
				1335	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				1336	<dd>Get a const_iterator that starts at the beginning of a type plane.
				1337	The iterator will iterate over the name/value pairs in the type plane.
				1338	Note: The type plane must already exist before using this.</dd>
				1339
				1340	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				1341	<dd>Get an iterator to the end of a type plane. This serves as the marker
				1342	for end of iteration of the type plane.
				1343	Note: The type plane must already exist before using this.</dd>
				1344
				1345	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				1346	<dd>Get a const_iterator to the end of a type plane. This serves as the
				1347	marker for end of iteration of the type plane.
				1348	Note: the type plane must already exist before using this.</dd>
				1349
				1350	<dt><tt>type_iterator type_begin()</tt>:</dt>
				1351	<dd>Get an iterator to the start of the name/Type map.</dd>
				1352
				1353	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				1354	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				1355
				1356	<dt><tt>type_iterator type_end()</tt>:</dt>
				1357	<dd>Get an iterator to the end of the name/Type map. This serves as the
				1358	marker for end of iteration of the types.</dd>
				1359
				1360	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				1361	<dd>Get a const-iterator to the end of the name/Type map. This serves
				1362	as the marker for end of iteration of the types.</dd>
				1363
				1364	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				1365	<dd>This method returns a plane_const_iterator for iteration over
				1366	the type planes starting at a specific plane, given by \p Ty.</dd>
				1367
				1368	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				1369	<dd>This method returns a plane_iterator for iteration over the
				1370	type planes starting at a specific plane, given by \p Ty.</dd>
				1371
				1372	</dl>
				1373	</div>
				1374
				1375
				1376
				1377	<!-- *********************************************************************** -->
				1378	<div class="doc_section">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1379	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				1380	</div>
				1381	<!-- *********************************************************************** -->
				1382
				1383	<div class="doc_text">
				1384
				1385	<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]	1386	being inspected or transformed. The core LLVM classes are defined in
				1387	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1388	the <tt>lib/VMCore</tt> directory.</p>
				1389
				1390	</div>
				1391
				1392	<!-- ======================================================================= -->
				1393	<div class="doc_subsection">
				1394	<a name="Value">The <tt>Value</tt> class</a>
				1395	</div>
				1396
				1397	<div>
				1398
				1399	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				1400	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1401	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]	1402
				1403	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				1404	base. It represents a typed value that may be used (among other things) as an
				1405	operand to an instruction. There are many different types of <tt>Value</tt>s,
				1406	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				1407	href="#Argument"><tt>Argument</tt></a>s. Even <a
				1408	href="#Instruction"><tt>Instruction</tt></a>s and <a
				1409	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				1410
				1411	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				1412	for a program. For example, an incoming argument to a function (represented
				1413	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				1414	every instruction in the function that references the argument. To keep track
				1415	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				1416	href="#User"><tt>User</tt></a>s that is using it (the <a
				1417	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				1418	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				1419	def-use information in the program, and is accessible through the <tt>use_</tt>*
				1420	methods, shown below.</p>
				1421
				1422	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				1423	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				1424	method. In addition, all LLVM values can be named. The "name" of the
				1425	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				1426
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1427	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1428
				1429	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				1430	that the name of any value may be missing (an empty string), so names should
				1431	<b>ONLY</b> be used for debugging (making the source code easier to read,
				1432	debugging printouts), they should not be used to keep track of values or map
				1433	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				1434	<tt>Value</tt> itself instead.</p>
				1435
				1436	<p>One important aspect of LLVM is that there is no distinction between an SSA
				1437	variable and the operation that produces it. Because of this, any reference to
				1438	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]	1439	argument, for example) is represented as a direct pointer to the instance of
				1440	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1441	represents this value. Although this may take some getting used to, it
				1442	simplifies the representation and makes it easier to manipulate.</p>
				1443
				1444	</div>
				1445
				1446	<!-- _______________________________________________________________________ -->
				1447	<div class="doc_subsubsection">
				1448	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				1449	</div>
				1450
				1451	<div class="doc_text">
				1452
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1453	<ul>
				1454	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1455	use-list<br>
				1456	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1457	the use-list<br>
				1458	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1459	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1460	<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]	1461	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1462	the use-list.<br>
				1463	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1464	use-list.<br>
				1465	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1466	element in the list.
				1467	<p> These methods are the interface to access the def-use
				1468	information in LLVM. As with all other iterators in LLVM, the naming
				1469	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]	1470	</li>
				1471	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1472	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1473	</li>
				1474	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1475	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1476	<tt>void setName(const std::string &Name)</tt>
				1477	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1478	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1479	</li>
				1480	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1481
				1482	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1483	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1484	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1485	produces a constant value (for example through constant folding), you can
				1486	replace all uses of the instruction with the constant like this:</p>
				1487
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1488	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1489	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1490
				1491	</div>
				1492
				1493	<!-- ======================================================================= -->
				1494	<div class="doc_subsection">
				1495	<a name="User">The <tt>User</tt> class</a>
				1496	</div>
				1497
				1498	<div class="doc_text">
				1499
				1500	<p>
				1501	<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]	1502	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]	1503	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1504
				1505	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1506	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1507	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1508	referring to. The <tt>User</tt> class itself is a subclass of
				1509	<tt>Value</tt>.</p>
				1510
				1511	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1512	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1513	Single Assignment (SSA) form, there can only be one definition referred to,
				1514	allowing this direct connection. This connection provides the use-def
				1515	information in LLVM.</p>
				1516
				1517	</div>
				1518
				1519	<!-- _______________________________________________________________________ -->
				1520	<div class="doc_subsubsection">
				1521	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1522	</div>
				1523
				1524	<div class="doc_text">
				1525
				1526	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1527	an index access interface and through an iterator based interface.</p>
				1528
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1529	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1530	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1531	<tt>unsigned getNumOperands()</tt>
				1532	<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]	1533	convenient form for direct access.</p></li>
				1534
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1535	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1536	list<br>
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	1537	<tt>op_iterator op_begin()</tt> - Get an iterator to the start of
				1538	the operand list.<br>
				1539	<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]	1540	operand list.
				1541	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1542	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1543	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1544
				1545	</div>
				1546
				1547	<!-- ======================================================================= -->
				1548	<div class="doc_subsection">
				1549	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1550	</div>
				1551
				1552	<div class="doc_text">
				1553
				1554	<p><tt>#include "</tt><tt><a
				1555	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1556	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]	1557	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1558	href="#Value"><tt>Value</tt></a></p>
				1559
				1560	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1561	instructions. It provides only a few methods, but is a very commonly used
				1562	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1563	opcode (instruction type) and the parent <a
				1564	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1565	into. To represent a specific type of instruction, one of many subclasses of
				1566	<tt>Instruction</tt> are used.</p>
				1567
				1568	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1569	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1570	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1571	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1572	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1573	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1574	file contains some meta-data about the various different types of instructions
				1575	in LLVM. It describes the enum values that are used as opcodes (for example
				1576	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1577	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1578	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1579	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1580	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]	1581	<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1582
				1583	</div>
				1584
				1585	<!-- _______________________________________________________________________ -->
				1586	<div class="doc_subsubsection">
				1587	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1588	class</a>
				1589	</div>
				1590
				1591	<div class="doc_text">
				1592
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1593	<ul>
				1594	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1595	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1596	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1597	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1598	<p>Returns true if the instruction writes to memory, i.e. it is a
				1599	<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]	1600	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1601	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1602	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1603	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1604	in all ways to the original except that the instruction has no parent
				1605	(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]	1606	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1607	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1608
				1609	</div>
				1610
				1611	<!-- ======================================================================= -->
				1612	<div class="doc_subsection">
				1613	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1614	</div>
				1615
				1616	<div class="doc_text">
				1617
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1618	<p><tt>#include "<a
				1619	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1620	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1621	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1622	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1623
				1624	<p>This class represents a single entry multiple exit section of the code,
				1625	commonly known as a basic block by the compiler community. The
				1626	<tt>BasicBlock</tt> class maintains a list of <a
				1627	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1628	Matching the language definition, the last element of this list of instructions
				1629	is always a terminator instruction (a subclass of the <a
				1630	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1631
				1632	<p>In addition to tracking the list of instructions that make up the block, the
				1633	<tt>BasicBlock</tt> class also keeps track of the <a
				1634	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1635
				1636	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1637	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1638	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1639	<tt>label</tt>.</p>
				1640
				1641	</div>
				1642
				1643	<!-- _______________________________________________________________________ -->
				1644	<div class="doc_subsubsection">
				1645	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1646	class</a>
				1647	</div>
				1648
				1649	<div class="doc_text">
				1650
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1651	<ul>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1652
				1653	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1654	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1655
				1656	<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1657	insertion into a function. The constructor optionally takes a name for the new
				1658	block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
				1659	the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
				1660	automatically inserted at the end of the specified <a
				1661	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1662	manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
				1663
				1664	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1665	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1666	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	1667	<tt>size()</tt>, <tt>empty()</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1668	STL-style functions for accessing the instruction list.
				1669
				1670	<p>These methods and typedefs are forwarding functions that have the same
				1671	semantics as the standard library methods of the same names. These methods
				1672	expose the underlying instruction list of a basic block in a way that is easy to
				1673	manipulate. To get the full complement of container operations (including
				1674	operations to update the list), you must use the <tt>getInstList()</tt>
				1675	method.</p></li>
				1676
				1677	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1678
				1679	<p>This method is used to get access to the underlying container that actually
				1680	holds the Instructions. This method must be used when there isn't a forwarding
				1681	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1682	to perform. Because there are no forwarding functions for "updating"
				1683	operations, you need to use this if you want to update the contents of a
				1684	<tt>BasicBlock</tt>.</p></li>
				1685
				1686	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1687
				1688	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1689	embedded into, or a null pointer if it is homeless.</p></li>
				1690
				1691	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1692
				1693	<p> Returns a pointer to the terminator instruction that appears at the end of
				1694	the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1695	instruction in the block is not a terminator, then a null pointer is
				1696	returned.</p></li>
				1697
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1698	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1699
				1700	</div>
				1701
				1702	<!-- ======================================================================= -->
				1703	<div class="doc_subsection">
				1704	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1705	</div>
				1706
				1707	<div class="doc_text">
				1708
				1709	<p><tt>#include "<a
				1710	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1711	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1712	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1713	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1714	href="#Value"><tt>Value</tt></a></p>
				1715
				1716	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1717	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1718	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1719	Because they are visible at global scope, they are also subject to linking with
				1720	other globals defined in different translation units. To control the linking
				1721	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1722	<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]	1723	defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1724
				1725	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1726	<tt>static</tt> in C), it is not visible to code outside the current translation
				1727	unit, and does not participate in linking. If it has external linkage, it is
				1728	visible to external code, and does participate in linking. In addition to
				1729	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1730	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1731
				1732	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1733	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1734	global is always a pointer to its contents. It is important to remember this
				1735	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1736	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1737	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1738	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1739	the address of the first element of this array and the value of the
				1740	<tt>GlobalVariable</tt> are the same, they have different types. The
				1741	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1742	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1743	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1744	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1745	Language Reference Manual</a>.</p>
				1746
				1747	</div>
				1748
				1749	<!-- _______________________________________________________________________ -->
				1750	<div class="doc_subsubsection">
				1751	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1752	class</a>
				1753	</div>
				1754
				1755	<div class="doc_text">
				1756
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1757	<ul>
				1758	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1759	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1760	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1761	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1762	<p> </p>
				1763	</li>
				1764	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1765	<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]	1766	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1767	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1768
				1769	</div>
				1770
				1771	<!-- ======================================================================= -->
				1772	<div class="doc_subsection">
				1773	<a name="Function">The <tt>Function</tt> class</a>
				1774	</div>
				1775
				1776	<div class="doc_text">
				1777
				1778	<p><tt>#include "<a
				1779	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]	1780	info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
				1781	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1782	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1783
				1784	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1785	actually one of the more complex classes in the LLVM heirarchy because it must
				1786	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1787	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1788	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1789	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1790
				1791	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1792	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1793	ordering of the blocks in the function, which indicate how the code will be
				1794	layed out by the backend. Additionally, the first <a
				1795	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1796	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1797	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1798	nodes from a single <tt>Function</tt>. If the <a
				1799	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1800	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1801	function hasn't been linked in yet.</p>
				1802
				1803	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1804	<tt>Function</tt> class also keeps track of the list of formal <a
				1805	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1806	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1807	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1808	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1809
				1810	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1811	LLVM feature that is only used when you have to look up a value by name. Aside
				1812	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1813	internally to make sure that there are not conflicts between the names of <a
				1814	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1815	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1816	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1817
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1818	<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
				1819	and therefore also a <a href="#Constant">Constant</a>. The value of the function
				1820	is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1821	</div>
				1822
				1823	<!-- _______________________________________________________________________ -->
				1824	<div class="doc_subsubsection">
				1825	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1826	class</a>
				1827	</div>
				1828
				1829	<div class="doc_text">
				1830
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1831	<ul>
				1832	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1833	Ty, LinkageTypes Linkage, const std::string &N = "", Module Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1834
				1835	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1836	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]	1837	create and what type of linkage the function should have. The <a
				1838	href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1839	specifies the formal arguments and return value for the function. The same
				1840	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1841	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1842	in which the function is defined. If this argument is provided, the function
				1843	will automatically be inserted into that module's list of
				1844	functions.</p></li>
				1845
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1846	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1847
				1848	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1849	function is "external", it does not have a body, and thus must be resolved
				1850	by linking with a function defined in a different translation unit.</p></li>
				1851
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1852	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1853	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1854
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	1855	<tt>begin()</tt>, <tt>end()</tt>
				1856	<tt>size()</tt>, <tt>empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1857
				1858	<p>These are forwarding methods that make it easy to access the contents of
				1859	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1860	list.</p></li>
				1861
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1862	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1863
				1864	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1865	is necessary to use when you need to update the list or perform a complex
				1866	action that doesn't have a forwarding method.</p></li>
				1867
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	1868	<li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1869	iterator<br>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	1870	<tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1871
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	1872	<tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	1873	<tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1874
				1875	<p>These are forwarding methods that make it easy to access the contents of
				1876	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1877	list.</p></li>
				1878
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1879	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1880
				1881	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1882	necessary to use when you need to update the list or perform a complex
				1883	action that doesn't have a forwarding method.</p></li>
				1884
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1885	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1886
				1887	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1888	function. Because the entry block for the function is always the first
				1889	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1890
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1891	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1892	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1893
				1894	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1895	<tt>Function</tt> and returns the return type of the function, or the <a
				1896	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1897	function.</p></li>
				1898
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1899	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1900
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1901	<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]	1902	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1903	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1904
				1905	</div>
				1906
				1907	<!-- ======================================================================= -->
				1908	<div class="doc_subsection">
				1909	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1910	</div>
				1911
				1912	<div class="doc_text">
				1913
				1914	<p><tt>#include "<a
				1915	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1916	<br>
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1917	doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1918	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1919	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1920
				1921	<p>Global variables are represented with the (suprise suprise)
				1922	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1923	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1924	always referenced by their address (global values must live in memory, so their
				1925	"name" refers to their address). See <a
				1926	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1927	may have an initial value (which must be a <a
				1928	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1929	may be marked as "constant" themselves (indicating that their contents never
				1930	change at runtime).</p>
				1931
				1932	</div>
				1933
				1934	<!-- _______________________________________________________________________ -->
				1935	<div class="doc_subsubsection">
				1936	<a name="m_GlobalVariable">Important Public Members of the
				1937	<tt>GlobalVariable</tt> class</a>
				1938	</div>
				1939
				1940	<div class="doc_text">
				1941
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1942	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1943	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1944	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1945	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1946
				1947	<p>Create a new global variable of the specified type. If
				1948	<tt>isConstant</tt> is true then the global variable will be marked as
				1949	unchanging for the program. The Linkage parameter specifies the type of
				1950	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1951	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1952	the resultant global variable will have internal linkage. AppendingLinkage
				1953	concatenates together all instances (in different translation units) of the
				1954	variable into a single variable but is only applicable to arrays.  See
				1955	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1956	further details on linkage types. Optionally an initializer, a name, and the
				1957	module to put the variable into may be specified for the global variable as
				1958	well.</p></li>
				1959
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1960	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1961
				1962	<p>Returns true if this is a global variable that is known not to
				1963	be modified at runtime.</p></li>
				1964
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1965	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1966
				1967	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1968
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1969	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1970
				1971	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1972	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1973	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1974
				1975	</div>
				1976
				1977	<!-- ======================================================================= -->
				1978	<div class="doc_subsection">
				1979	<a name="Module">The <tt>Module</tt> class</a>
				1980	</div>
				1981
				1982	<div class="doc_text">
				1983
				1984	<p><tt>#include "<a
				1985	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]	1986	<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1987
				1988	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1989	programs. An LLVM module is effectively either a translation unit of the
				1990	original program or a combination of several translation units merged by the
				1991	linker. The <tt>Module</tt> class keeps track of a list of <a
				1992	href="#Function"><tt>Function</tt></a>s, a list of <a
				1993	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1994	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1995	helpful member functions that try to make common operations easy.</p>
				1996
				1997	</div>
				1998
				1999	<!-- _______________________________________________________________________ -->
				2000	<div class="doc_subsubsection">
				2001	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				2002	</div>
				2003
				2004	<div class="doc_text">
				2005
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2006	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2007	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2008	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2009
				2010	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				2011	provide a name for it (probably based on the name of the translation unit).</p>
				2012
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2013	<ul>
				2014	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	2015	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2016
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	2017	<tt>begin()</tt>, <tt>end()</tt>
				2018	<tt>size()</tt>, <tt>empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2019
				2020	<p>These are forwarding methods that make it easy to access the contents of
				2021	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				2022	list.</p></li>
				2023
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2024	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2025
				2026	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				2027	necessary to use when you need to update the list or perform a complex
				2028	action that doesn't have a forwarding method.</p>
				2029
				2030	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2031	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2032
				2033	<hr>
				2034
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2035	<ul>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	2036	<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]	2037
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	2038	<tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2039
Chris Lattner	77d6924	2005-03-15 05:19:20 +0000	[diff] [blame]	2040	<tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner	89cc265	2005-03-15 04:48:32 +0000	[diff] [blame]	2041	<tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2042
				2043	<p> These are forwarding methods that make it easy to access the contents of
				2044	a <tt>Module</tt> object's <a
				2045	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				2046
				2047	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				2048
				2049	<p>Returns the list of <a
				2050	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				2051	use when you need to update the list or perform a complex action that
				2052	doesn't have a forwarding method.</p>
				2053
				2054	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2055	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2056
				2057	<hr>
				2058
				2059	<ul>
				2060	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				2061
				2062	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				2063	for this <tt>Module</tt>.</p>
				2064
				2065	<p><!-- Convenience methods --></p></li>
				2066	</ul>
				2067
				2068	<hr>
				2069
				2070	<ul>
				2071	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				2072	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				2073
				2074	<p>Look up the specified function in the <tt>Module</tt> <a
				2075	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				2076	<tt>null</tt>.</p></li>
				2077
				2078	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				2079	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				2080
				2081	<p>Look up the specified function in the <tt>Module</tt> <a
				2082	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				2083	external declaration for the function and return it.</p></li>
				2084
				2085	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				2086
				2087	<p>If there is at least one entry in the <a
				2088	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				2089	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				2090	string.</p></li>
				2091
				2092	<li><tt>bool addTypeName(const std::string &Name, const <a
				2093	href="#Type">Type</a> *Ty)</tt>
				2094
				2095	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				2096	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				2097	name, true is returned and the <a
				2098	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				2099	</ul>
				2100
				2101	</div>
				2102
				2103	<!-- ======================================================================= -->
				2104	<div class="doc_subsection">
				2105	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				2106	</div>
				2107
				2108	<div class="doc_text">
				2109
				2110	<p>Constant represents a base class for different types of constants. It
				2111	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				2112	ConstantArray etc for representing the various types of Constants.</p>
				2113
				2114	</div>
				2115
				2116	<!-- _______________________________________________________________________ -->
				2117	<div class="doc_subsubsection">
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2118	<a name="m_Constant">Important Public Methods</a>
				2119	</div>
				2120	<div class="doc_text">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2121	</div>
				2122
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2123	<!-- _______________________________________________________________________ -->
				2124	<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2125	<div class="doc_text">
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2126	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2127	<li>ConstantSInt : This subclass of Constant represents a signed integer
				2128	constant.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2129	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2130	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				2131	this constant. </li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2132	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2133	</li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2134	<li>ConstantUInt : This class represents an unsigned integer.
				2135	<ul>
				2136	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
				2137	this constant. </li>
				2138	</ul>
				2139	</li>
				2140	<li>ConstantFP : This class represents a floating point constant.
				2141	<ul>
				2142	<li><tt>double getValue() const</tt>: Returns the underlying value of
				2143	this constant. </li>
				2144	</ul>
				2145	</li>
				2146	<li>ConstantBool : This represents a boolean constant.
				2147	<ul>
				2148	<li><tt>bool getValue() const</tt>: Returns the underlying value of this
				2149	constant. </li>
				2150	</ul>
				2151	</li>
				2152	<li>ConstantArray : This represents a constant array.
				2153	<ul>
				2154	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	2155	a vector of component constants that makeup this array. </li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2156	</ul>
				2157	</li>
				2158	<li>ConstantStruct : This represents a constant struct.
				2159	<ul>
				2160	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	2161	a vector of component constants that makeup this array. </li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	2162	</ul>
				2163	</li>
				2164	<li>GlobalValue : This represents either a global variable or a function. In
				2165	either case, the value is a constant fixed address (after linking).
				2166	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2167	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2168	</div>
				2169
				2170	<!-- ======================================================================= -->
				2171	<div class="doc_subsection">
				2172	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				2173	</div>
				2174
				2175	<div class="doc_text">
				2176
				2177	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				2178	type (like int, short etc) in LLVM is an instance of Type Class. All other
				2179	types are instances of subclasses of type like FunctionType, ArrayType
				2180	etc. DerivedType is the interface for all such dervied types including
				2181	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				2182	be recursive (StructType). There exists exactly one instance of any type
				2183	structure at a time. This allows using pointer equality of Type *s for comparing
				2184	types.</p>
				2185
				2186	</div>
				2187
				2188	<!-- _______________________________________________________________________ -->
				2189	<div class="doc_subsubsection">
				2190	<a name="m_Value">Important Public Methods</a>
				2191	</div>
				2192
				2193	<div class="doc_text">
				2194
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2195	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2196
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2197	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				2198	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				2199	not true for Float and Double. </li>
				2200
				2201	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				2202	unsigned. This is not quite the complement of isSigned... nonnumeric types
				2203	return false as they do with isSigned. This returns true for UByteTy,
				2204	UShortTy, UIntTy, and ULongTy. </li>
				2205
Chris Lattner	4573f1b	2004-07-08 17:49:37 +0000	[diff] [blame]	2206	<li><tt>bool isInteger() const</tt>: Equivalent to isSigned() \|\| isUnsigned().</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2207
				2208	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				2209	type, which is either Bool type or one of the Integer types.</li>
				2210
				2211	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				2212	floating point types.</li>
				2213
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2214	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				2215	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]	2216	example, uint to int or one pointer type to another.</li>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	2217	</ul>
				2218	</div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2219
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	2220	<!-- _______________________________________________________________________ -->
				2221	<div class="doc_subsubsection">
				2222	<a name="m_Value">Important Derived Types</a>
				2223	</div>
				2224	<div class="doc_text">
				2225	<ul>
				2226	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2227	<ul>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	2228	<li><tt>const Type * getElementType() const</tt>: Returns the type of each
				2229	of the elements in the sequential type. </li>
				2230	</ul>
				2231	</li>
				2232	<li>ArrayType : This is a subclass of SequentialType and defines interface for
				2233	array types.
				2234	<ul>
				2235	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				2236	elements in the array. </li>
				2237	</ul>
				2238	</li>
				2239	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				2240	<li>StructType : subclass of DerivedTypes for struct types </li>
				2241	<li>FunctionType : subclass of DerivedTypes for function types.
				2242	<ul>
				2243	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				2244	function</li>
				2245	<li><tt> const Type * getReturnType() const</tt>: Returns the
				2246	return type of the function.</li>
				2247	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
				2248	the type of the ith parameter.</li>
				2249	<li><tt> const unsigned getNumParams() const</tt>: Returns the
				2250	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2251	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2252	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	2253	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2254	</div>
				2255
				2256	<!-- ======================================================================= -->
				2257	<div class="doc_subsection">
				2258	<a name="Argument">The <tt>Argument</tt> class</a>
				2259	</div>
				2260
				2261	<div class="doc_text">
				2262
				2263	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame]	2264	arguments to a function. A Function maintains a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2265	arguments. An argument has a pointer to the parent Function.</p>
				2266
				2267	</div>
				2268
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2269	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2270	<hr>
				2271	<address>
				2272	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2273	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2274	<a href="http://validator.w3.org/check/referer"><img
				2275	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2276
				2277	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2278	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2279	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2280	Last modified: $Date$
				2281	</address>
				2282
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2283	</body>
				2284	</html>