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