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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
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				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
				18	<li><a href="#stl">The C++ Standard Template Library</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	19	<li>The <tt>-time-passes</tt> option
				20	<li>How to use the LLVM Makefile system
				21	<li>How to write a regression test
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	22	--> </li>
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	23	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	24	</li>
				25	<li><a href="#apis">Important and useful LLVM APIs</a>
				26	<ul>
				27	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				28	and <tt>dyn_cast<></tt> templates</a> </li>
				29	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				30	option</a>
				31	<ul>
				32	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				33	and the <tt>-debug-only</tt> option</a> </li>
				34	</ul>
				35	</li>
				36	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				37	option</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	38	<li>The <tt>InstVisitor</tt> template
				39	<li>The general graph API
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	40	--> </li>
				41	</ul>
				42	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	43	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	44	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	45	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				46	<ul>
				47	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				48	in a <tt>Function</tt></a> </li>
				49	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				50	in a <tt>BasicBlock</tt></a> </li>
				51	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				52	in a <tt>Function</tt></a> </li>
				53	<li><a href="#iterate_convert">Turning an iterator into a
				54	class pointer</a> </li>
				55	<li><a href="#iterate_complex">Finding call sites: a more
				56	complex example</a> </li>
				57	<li><a href="#calls_and_invokes">Treating calls and invokes
				58	the same way</a> </li>
				59	<li><a href="#iterate_chains">Iterating over def-use &
				60	use-def chains</a> </li>
				61	</ul>
				62	</li>
				63	<li><a href="#simplechanges">Making simple changes</a>
				64	<ul>
				65	<li><a href="#schanges_creating">Creating and inserting new
				66	<tt>Instruction</tt>s</a> </li>
				67	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				68	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				69	with another <tt>Value</tt></a> </li>
				70	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	71	<!--
				72	<li>Working with the Control Flow Graph
				73	<ul>
				74	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				75	<li>
				76	<li>
				77	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	78	--> </li>
				79	</ul>
				80	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	81	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	82	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	83	<li><a href="#Value">The <tt>Value</tt> class</a>
				84	<ul>
				85	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	86	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	87	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	88	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	89	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt>
				90	class</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	91	</ul></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	92	<li><a href="#Module">The <tt>Module</tt> class</a></li>
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	93	<li><a href="#Constant">The <tt>Constant</tt> class</a>
				94	<ul>
				95	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				96	<ul>
				97	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				98	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				99	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class
				100	</a></li>
				101	</ul></li>
				102	</ul>
				103	</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	104	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	105	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
				106	</ul></li>
				107	</ul></li>
				108	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				109	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				110	<ul>
				111	<li>Creating, inserting, moving and deleting from LLVM lists </li>
				112	</ul>
				113	</li>
				114	<li>Important iterator invalidation semantics to be aware of.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	115	</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	116	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	117
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	118	<div class="doc_author">
				119	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner	94c4359	2004-05-26 16:52:55 +0000	[diff] [blame]	120	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
				121	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
				122	<a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	123	</div>
				124
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	125	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	126	<div class="doc_section">
				127	<a name="introduction">Introduction </a>
				128	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	129	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	130
				131	<div class="doc_text">
				132
				133	<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]	134	interfaces available in the LLVM source-base. This manual is not
				135	intended to explain what LLVM is, how it works, and what LLVM code looks
				136	like. It assumes that you know the basics of LLVM and are interested
				137	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	138	code.</p>
				139
				140	<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]	141	way in the continuously growing source code that makes up the LLVM
				142	infrastructure. Note that this manual is not intended to serve as a
				143	replacement for reading the source code, so if you think there should be
				144	a method in one of these classes to do something, but it's not listed,
				145	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				146	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	147
				148	<p>The first section of this document describes general information that is
				149	useful to know when working in the LLVM infrastructure, and the second describes
				150	the Core LLVM classes. In the future this manual will be extended with
				151	information describing how to use extension libraries, such as dominator
				152	information, CFG traversal routines, and useful utilities like the <tt><a
				153	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				154
				155	</div>
				156
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	157	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	158	<div class="doc_section">
				159	<a name="general">General Information</a>
				160	</div>
				161	<!-- *********************************************************************** -->
				162
				163	<div class="doc_text">
				164
				165	<p>This section contains general information that is useful if you are working
				166	in the LLVM source-base, but that isn't specific to any particular API.</p>
				167
				168	</div>
				169
				170	<!-- ======================================================================= -->
				171	<div class="doc_subsection">
				172	<a name="stl">The C++ Standard Template Library</a>
				173	</div>
				174
				175	<div class="doc_text">
				176
				177	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	178	perhaps much more than you are used to, or have seen before. Because of
				179	this, you might want to do a little background reading in the
				180	techniques used and capabilities of the library. There are many good
				181	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]	182	can get, so it will not be discussed in this document.</p>
				183
				184	<p>Here are some useful links:</p>
				185
				186	<ol>
				187
				188	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				189	reference</a> - an excellent reference for the STL and other parts of the
				190	standard C++ library.</li>
				191
				192	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Tanya Lattner	09cf73c	2004-06-22 04:24:55 +0000	[diff] [blame]	193	O'Reilly book in the making. It has a decent
				194	Standard Library
				195	Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	196	published.</li>
				197
				198	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				199	Questions</a></li>
				200
				201	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				202	Contains a useful <a
				203	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				204	STL</a>.</li>
				205
				206	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				207	Page</a></li>
				208
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	209	<li><a href="http://www.linux.com.cn/Bruce_Eckel/TICPPv2/Contents.htm">
				210	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				211	the book).</a></li>
				212
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	213	</ol>
				214
				215	<p>You are also encouraged to take a look at the <a
				216	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				217	to write maintainable code more than where to put your curly braces.</p>
				218
				219	</div>
				220
				221	<!-- ======================================================================= -->
				222	<div class="doc_subsection">
				223	<a name="stl">Other useful references</a>
				224	</div>
				225
				226	<div class="doc_text">
				227
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	228	<ol>
				229	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	230	Branch and Tag Primer</a></li>
Misha Brukman	a0f71e4	2004-06-18 18:39:00 +0000	[diff] [blame]	231	<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
				232	static and shared libraries across platforms</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	233	</ol>
				234
				235	</div>
				236
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	237	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	238	<div class="doc_section">
				239	<a name="apis">Important and useful LLVM APIs</a>
				240	</div>
				241	<!-- *********************************************************************** -->
				242
				243	<div class="doc_text">
				244
				245	<p>Here we highlight some LLVM APIs that are generally useful and good to
				246	know about when writing transformations.</p>
				247
				248	</div>
				249
				250	<!-- ======================================================================= -->
				251	<div class="doc_subsection">
				252	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				253	</div>
				254
				255	<div class="doc_text">
				256
				257	<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]	258	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				259	operator, but they don't have some drawbacks (primarily stemming from
				260	the fact that <tt>dynamic_cast<></tt> only works on classes that
				261	have a v-table). Because they are used so often, you must know what they
				262	do and how they work. All of these templates are defined in the <a
				263	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	264	file (note that you very rarely have to include this file directly).</p>
				265
				266	<dl>
				267	<dt><tt>isa<></tt>: </dt>
				268
				269	<dd>The <tt>isa<></tt> operator works exactly like the Java
				270	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				271	a reference or pointer points to an instance of the specified class. This can
				272	be very useful for constraint checking of various sorts (example below).</dd>
				273
				274	<dt><tt>cast<></tt>: </dt>
				275
				276	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				277	converts a pointer or reference from a base class to a derived cast, causing
				278	an assertion failure if it is not really an instance of the right type. This
				279	should be used in cases where you have some information that makes you believe
				280	that something is of the right type. An example of the <tt>isa<></tt>
				281	and <tt>cast<></tt> template is:
				282
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	283	<pre>
				284	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				285	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				286	return true;
				287
				288	<i>// Otherwise, it must be an instruction...</i>
				289	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				290	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	291
				292	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				293	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				294	operator.</p>
				295
				296	</dd>
				297
				298	<dt><tt>dyn_cast<></tt>:</dt>
				299
				300	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				301	checks to see if the operand is of the specified type, and if so, returns a
				302	pointer to it (this operator does not work with references). If the operand is
				303	not of the correct type, a null pointer is returned. Thus, this works very
				304	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				305	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				306	in an <tt>if</tt> statement or some other flow control statement like this:
				307
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	308	<pre>
				309	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				310	...
				311	}
				312	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	313
				314	<p> This form of the <tt>if</tt> statement effectively combines together a
				315	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				316	statement, which is very convenient.</p>
				317
				318	<p> Another common example is:</p>
				319
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	320	<pre>
				321	<i>// Loop over all of the phi nodes in a basic block</i>
				322	BasicBlock::iterator BBI = BB->begin();
				323	for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(BBI); ++BBI)
				324	std::cerr << *PN;
				325	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	326
				327	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				328	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				329	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				330	check for lots of different variants of classes. If you find yourself
				331	wanting to do this, it is much cleaner and more efficient to use the
				332	InstVisitor class to dispatch over the instruction type directly.</p>
				333
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	334	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	335
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	336	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	337
				338	<dd>The <tt>cast_or_null<></tt> operator works just like the
				339	<tt>cast<></tt> operator, except that it allows for a null pointer as
				340	an argument (which it then propagates). This can sometimes be useful,
				341	allowing you to combine several null checks into one.</dd>
				342
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	343	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	344
				345	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				346	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				347	as an argument (which it then propagates). This can sometimes be useful,
				348	allowing you to combine several null checks into one.</dd>
				349
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	350	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	351
				352	<p>These five templates can be used with any classes, whether they have a
				353	v-table or not. To add support for these templates, you simply need to add
				354	<tt>classof</tt> static methods to the class you are interested casting
				355	to. Describing this is currently outside the scope of this document, but there
				356	are lots of examples in the LLVM source base.</p>
				357
				358	</div>
				359
				360	<!-- ======================================================================= -->
				361	<div class="doc_subsection">
				362	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				363	</div>
				364
				365	<div class="doc_text">
				366
				367	<p>Often when working on your pass you will put a bunch of debugging printouts
				368	and other code into your pass. After you get it working, you want to remove
				369	it... but you may need it again in the future (to work out new bugs that you run
				370	across).</p>
				371
				372	<p> Naturally, because of this, you don't want to delete the debug printouts,
				373	but you don't want them to always be noisy. A standard compromise is to comment
				374	them out, allowing you to enable them if you need them in the future.</p>
				375
				376	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				377	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				378	this problem. Basically, you can put arbitrary code into the argument of the
				379	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				380	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				381
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	382	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	383
				384	<p>Then you can run your pass like this:</p>
				385
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	386	<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]	387
				388	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				389	to not have to create "yet another" command line option for the debug output for
				390	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				391	so they do not cause a performance impact at all (for the same reason, they
				392	should also not contain side-effects!).</p>
				393
				394	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				395	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				396	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				397	program hasn't been started yet, you can always just run it with
				398	<tt>-debug</tt>.</p>
				399
				400	</div>
				401
				402	<!-- _______________________________________________________________________ -->
				403	<div class="doc_subsubsection">
				404	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				405	the <tt>-debug-only</tt> option</a>
				406	</div>
				407
				408	<div class="doc_text">
				409
				410	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				411	just turns on <b>too much</b> information (such as when working on the code
				412	generator). If you want to enable debug information with more fine-grained
				413	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				414	option as follows:</p>
				415
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	416	<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]	417
				418	<p>Then you can run your pass like this:</p>
				419
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	420	<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]	421
				422	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				423	a file, to specify the debug type for the entire module (if you do this before
				424	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				425	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				426	"bar", because there is no system in place to ensure that names do not
				427	conflict. If two different modules use the same string, they will all be turned
				428	on when the name is specified. This allows, for example, all debug information
				429	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	430	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	431
				432	</div>
				433
				434	<!-- ======================================================================= -->
				435	<div class="doc_subsection">
				436	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				437	option</a>
				438	</div>
				439
				440	<div class="doc_text">
				441
				442	<p>The "<tt><a
				443	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				444	provides a template named <tt>Statistic</tt> that is used as a unified way to
				445	keep track of what the LLVM compiler is doing and how effective various
				446	optimizations are. It is useful to see what optimizations are contributing to
				447	making a particular program run faster.</p>
				448
				449	<p>Often you may run your pass on some big program, and you're interested to see
				450	how many times it makes a certain transformation. Although you can do this with
				451	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				452	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				453	keep track of this information, and the calculated information is presented in a
				454	uniform manner with the rest of the passes being executed.</p>
				455
				456	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				457	it are as follows:</p>
				458
				459	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	460	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	461	<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]	462
				463	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				464	but if you do not specify a template argument, it defaults to acting like
				465	an unsigned int counter (this is usually what you want).</p></li>
				466
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	467	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	468	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	469	</li>
				470	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	471
				472	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				473	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				474
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	475	<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]	476
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	477	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				478	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	479
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	480	<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]	481
				482	<p>Obviously, with so many optimizations, having a unified framework for this
				483	stuff is very nice. Making your pass fit well into the framework makes it more
				484	maintainable and useful.</p>
				485
				486	</div>
				487
				488	<!-- *********************************************************************** -->
				489	<div class="doc_section">
				490	<a name="common">Helpful Hints for Common Operations</a>
				491	</div>
				492	<!-- *********************************************************************** -->
				493
				494	<div class="doc_text">
				495
				496	<p>This section describes how to perform some very simple transformations of
				497	LLVM code. This is meant to give examples of common idioms used, showing the
				498	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				499	you should also read about the main classes that you will be working with. The
				500	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				501	and descriptions of the main classes that you should know about.</p>
				502
				503	</div>
				504
				505	<!-- NOTE: this section should be heavy on example code -->
				506	<!-- ======================================================================= -->
				507	<div class="doc_subsection">
				508	<a name="inspection">Basic Inspection and Traversal Routines</a>
				509	</div>
				510
				511	<div class="doc_text">
				512
				513	<p>The LLVM compiler infrastructure have many different data structures that may
				514	be traversed. Following the example of the C++ standard template library, the
				515	techniques used to traverse these various data structures are all basically the
				516	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				517	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				518	function returns an iterator pointing to one past the last valid element of the
				519	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				520	between the two operations.</p>
				521
				522	<p>Because the pattern for iteration is common across many different aspects of
				523	the program representation, the standard template library algorithms may be used
				524	on them, and it is easier to remember how to iterate. First we show a few common
				525	examples of the data structures that need to be traversed. Other data
				526	structures are traversed in very similar ways.</p>
				527
				528	</div>
				529
				530	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	531	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	532	<a name="iterate_function">Iterating over the </a><a
				533	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				534	href="#Function"><tt>Function</tt></a>
				535	</div>
				536
				537	<div class="doc_text">
				538
				539	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				540	transform in some way; in particular, you'd like to manipulate its
				541	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				542	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				543	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				544	<tt>Instruction</tt>s it contains:</p>
				545
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	546	<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]	547
				548	<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]	549	invoking member functions of the <tt>Instruction</tt> class. This is
				550	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	551	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	552	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				553
				554	</div>
				555
				556	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	557	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	558	<a name="iterate_basicblock">Iterating over the </a><a
				559	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				560	href="#BasicBlock"><tt>BasicBlock</tt></a>
				561	</div>
				562
				563	<div class="doc_text">
				564
				565	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				566	easy to iterate over the individual instructions that make up
				567	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				568	a <tt>BasicBlock</tt>:</p>
				569
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	570	<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]	571
				572	<p>However, this isn't really the best way to print out the contents of a
				573	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				574	anything you'll care about, you could have just invoked the print routine on the
				575	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				576
				577	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				578	it will print out the contents of the pointer, instead of the pointer value you
				579	might expect. This is a deprecated interface that will be removed in the
				580	future, so it's best not to depend on it. To print out the pointer value for
				581	now, you must cast to <tt>void*</tt>.</p>
				582
				583	</div>
				584
				585	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	586	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	587	<a name="iterate_institer">Iterating over the </a><a
				588	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				589	href="#Function"><tt>Function</tt></a>
				590	</div>
				591
				592	<div class="doc_text">
				593
				594	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				595	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				596	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				597	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				598	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]	599	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]	600
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	601	<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]	602	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				603	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	604	initialize a worklist to contain all instructions in a <tt>Function</tt>
				605	F, all you would need to do is something like:
				606	<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]	607
				608	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				609	<tt>Function</tt> pointed to by F.</p>
				610
				611	</div>
				612
				613	<!-- _______________________________________________________________________ -->
				614	<div class="doc_subsubsection">
				615	<a name="iterate_convert">Turning an iterator into a class pointer (and
				616	vice-versa)</a>
				617	</div>
				618
				619	<div class="doc_text">
				620
				621	<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]	622	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]	623	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	624	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]	625	is a <tt>BasicBlock::const_iterator</tt>:</p>
				626
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	627	<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]	628
				629	<p>However, the iterators you'll be working with in the LLVM framework are
				630	special: they will automatically convert to a ptr-to-instance type whenever they
				631	need to. Instead of dereferencing the iterator and then taking the address of
				632	the result, you can simply assign the iterator to the proper pointer type and
				633	you get the dereference and address-of operation as a result of the assignment
				634	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				635	the last line of the last example,</p>
				636
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	637	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	638
				639	<p>is semantically equivalent to</p>
				640
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	641	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	642
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	643	<p>It's also possible to turn a class pointer into the corresponding iterator,
				644	and this is a constant time operation (very efficient). The following code
				645	snippet illustrates use of the conversion constructors provided by LLVM
				646	iterators. By using these, you can explicitly grab the iterator of something
				647	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	648
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	649	<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]	650
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	651	</div>
				652
				653	<!--_______________________________________________________________________-->
				654	<div class="doc_subsubsection">
				655	<a name="iterate_complex">Finding call sites: a slightly more complex
				656	example</a>
				657	</div>
				658
				659	<div class="doc_text">
				660
				661	<p>Say that you're writing a FunctionPass and would like to count all the
				662	locations in the entire module (that is, across every <tt>Function</tt>) where a
				663	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				664	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]	665	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]	666	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				667	is what we want to do:</p>
				668
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	669	<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]	670
				671	<p>And the actual code is (remember, since we're writing a
				672	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				673	override the <tt>runOnFunction</tt> method...):</p>
				674
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	675	<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
				676	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				677	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]	678
				679	</div>
				680
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	681	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	682	<div class="doc_subsubsection">
				683	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				684	</div>
				685
				686	<div class="doc_text">
				687
				688	<p>You may have noticed that the previous example was a bit oversimplified in
				689	that it did not deal with call sites generated by 'invoke' instructions. In
				690	this, and in other situations, you may find that you want to treat
				691	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				692	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				693	less closely-related things. For these cases, LLVM provides a handy wrapper
				694	class called <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	695	href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	696	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				697	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	698	<tt>InvokeInst</tt>s.</p>
				699
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	700	<p>This class has "value semantics": it should be passed by value, not by
				701	reference and it should not be dynamically allocated or deallocated using
				702	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				703	assignable and constructable, with costs equivalents to that of a bare pointer.
				704	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]	705
				706	</div>
				707
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	708	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	709	<div class="doc_subsubsection">
				710	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				711	</div>
				712
				713	<div class="doc_text">
				714
				715	<p>Frequently, we might have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	716	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				717	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				718	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				719	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				720	particular function <tt>foo</tt>. Finding all of the instructions that
				721	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				722	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	723
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	724	<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]	725
				726	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	727	href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	728	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				729	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				730	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				731	all of the values that a particular instruction uses (that is, the operands of
				732	the particular <tt>Instruction</tt>):</p>
				733
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	734	<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]	735
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	736	<!--
				737	def-use chains ("finding all users of"): Value::use_begin/use_end
				738	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]	739	-->
				740
				741	</div>
				742
				743	<!-- ======================================================================= -->
				744	<div class="doc_subsection">
				745	<a name="simplechanges">Making simple changes</a>
				746	</div>
				747
				748	<div class="doc_text">
				749
				750	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	751	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	752	transformations, it's fairly common to manipulate the contents of basic
				753	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	754	and gives example code.</p>
				755
				756	</div>
				757
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	758	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	759	<div class="doc_subsubsection">
				760	<a name="schanges_creating">Creating and inserting new
				761	<tt>Instruction</tt>s</a>
				762	</div>
				763
				764	<div class="doc_text">
				765
				766	<p><i>Instantiating Instructions</i></p>
				767
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	768	<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]	769	constructor for the kind of instruction to instantiate and provide the necessary
				770	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				771	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				772
				773	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				774
				775	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				776	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				777	subclass is likely to have varying default parameters which change the semantics
				778	of the instruction, so refer to the <a
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	779	href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	780	Instruction</a> that you're interested in instantiating.</p>
				781
				782	<p><i>Naming values</i></p>
				783
				784	<p>It is very useful to name the values of instructions when you're able to, as
				785	this facilitates the debugging of your transformations. If you end up looking
				786	at generated LLVM machine code, you definitely want to have logical names
				787	associated with the results of instructions! By supplying a value for the
				788	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				789	associate a logical name with the result of the instruction's execution at
				790	runtime. For example, say that I'm writing a transformation that dynamically
				791	allocates space for an integer on the stack, and that integer is going to be
				792	used as some kind of index by some other code. To accomplish this, I place an
				793	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				794	<tt>Function</tt>, and I'm intending to use it within the same
				795	<tt>Function</tt>. I might do:</p>
				796
				797	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				798
				799	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				800	execution value, which is a pointer to an integer on the runtime stack.</p>
				801
				802	<p><i>Inserting instructions</i></p>
				803
				804	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				805	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				806
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	807	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	808	<li>Insertion into an explicit instruction list
				809
				810	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				811	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				812	before <tt>*pi</tt>, we do the following: </p>
				813
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	814	<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>
				815
				816	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				817	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				818	classes provide constructors which take a pointer to a
				819	<tt>BasicBlock</tt> to be appended to. For example code that
				820	looked like: </p>
				821
				822	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				823
				824	<p>becomes: </p>
				825
				826	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				827
				828	<p>which is much cleaner, especially if you are creating
				829	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	830
				831	<li>Insertion into an implicit instruction list
				832
				833	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				834	are implicitly associated with an existing instruction list: the instruction
				835	list of the enclosing basic block. Thus, we could have accomplished the same
				836	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				837	</p>
				838
				839	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				840
				841	<p>In fact, this sequence of steps occurs so frequently that the
				842	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				843	constructors which take (as a default parameter) a pointer to an
				844	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				845	precede. That is, <tt>Instruction</tt> constructors are capable of
				846	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				847	provided instruction, immediately before that instruction. Using an
				848	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				849	parameter, the above code becomes:</p>
				850
				851	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				852
				853	<p>which is much cleaner, especially if you're creating a lot of
				854	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				855	</ul>
				856
				857	</div>
				858
				859	<!--_______________________________________________________________________-->
				860	<div class="doc_subsubsection">
				861	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				862	</div>
				863
				864	<div class="doc_text">
				865
				866	<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]	867	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	868	you must have a pointer to the instruction that you wish to delete. Second, you
				869	need to obtain the pointer to that instruction's basic block. You use the
				870	pointer to the basic block to get its list of instructions and then use the
				871	erase function to remove your instruction. For example:</p>
				872
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	873	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				874	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]	875
				876	</div>
				877
				878	<!--_______________________________________________________________________-->
				879	<div class="doc_subsubsection">
				880	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				881	<tt>Value</tt></a>
				882	</div>
				883
				884	<div class="doc_text">
				885
				886	<p><i>Replacing individual instructions</i></p>
				887
				888	<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]	889	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	890	and <tt>ReplaceInstWithInst</tt>.</p>
				891
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	892	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	893
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	894	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	895	<li><tt>ReplaceInstWithValue</tt>
				896
				897	<p>This function replaces all uses (within a basic block) of a given
				898	instruction with a value, and then removes the original instruction. The
				899	following example illustrates the replacement of the result of a particular
				900	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				901	pointer to an integer.</p>
				902
				903	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				904
				905	<li><tt>ReplaceInstWithInst</tt>
				906
				907	<p>This function replaces a particular instruction with another
				908	instruction. The following example illustrates the replacement of one
				909	<tt>AllocaInst</tt> with another.</p>
				910
				911	<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]	912	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	913
				914	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				915
				916	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				917	<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	918	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				919	and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	920	information.</p>
				921
				922	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				923	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				924	ReplaceInstWithValue, ReplaceInstWithInst -->
				925
				926	</div>
				927
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	928	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	929	<div class="doc_section">
				930	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				931	</div>
				932	<!-- *********************************************************************** -->
				933
				934	<div class="doc_text">
				935
				936	<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]	937	being inspected or transformed. The core LLVM classes are defined in
				938	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	939	the <tt>lib/VMCore</tt> directory.</p>
				940
				941	</div>
				942
				943	<!-- ======================================================================= -->
				944	<div class="doc_subsection">
				945	<a name="Value">The <tt>Value</tt> class</a>
				946	</div>
				947
				948	<div>
				949
				950	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				951	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	952	doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	953
				954	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				955	base. It represents a typed value that may be used (among other things) as an
				956	operand to an instruction. There are many different types of <tt>Value</tt>s,
				957	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				958	href="#Argument"><tt>Argument</tt></a>s. Even <a
				959	href="#Instruction"><tt>Instruction</tt></a>s and <a
				960	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				961
				962	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				963	for a program. For example, an incoming argument to a function (represented
				964	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				965	every instruction in the function that references the argument. To keep track
				966	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				967	href="#User"><tt>User</tt></a>s that is using it (the <a
				968	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				969	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				970	def-use information in the program, and is accessible through the <tt>use_</tt>*
				971	methods, shown below.</p>
				972
				973	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				974	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				975	method. In addition, all LLVM values can be named. The "name" of the
				976	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				977
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	978	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	979
				980	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				981	that the name of any value may be missing (an empty string), so names should
				982	<b>ONLY</b> be used for debugging (making the source code easier to read,
				983	debugging printouts), they should not be used to keep track of values or map
				984	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				985	<tt>Value</tt> itself instead.</p>
				986
				987	<p>One important aspect of LLVM is that there is no distinction between an SSA
				988	variable and the operation that produces it. Because of this, any reference to
				989	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]	990	argument, for example) is represented as a direct pointer to the instance of
				991	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	992	represents this value. Although this may take some getting used to, it
				993	simplifies the representation and makes it easier to manipulate.</p>
				994
				995	</div>
				996
				997	<!-- _______________________________________________________________________ -->
				998	<div class="doc_subsubsection">
				999	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				1000	</div>
				1001
				1002	<div class="doc_text">
				1003
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1004	<ul>
				1005	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1006	use-list<br>
				1007	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1008	the use-list<br>
				1009	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1010	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1011	<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]	1012	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1013	the use-list.<br>
				1014	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1015	use-list.<br>
				1016	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1017	element in the list.
				1018	<p> These methods are the interface to access the def-use
				1019	information in LLVM. As with all other iterators in LLVM, the naming
				1020	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]	1021	</li>
				1022	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1023	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1024	</li>
				1025	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1026	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1027	<tt>void setName(const std::string &Name)</tt>
				1028	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1029	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1030	</li>
				1031	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1032
				1033	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1034	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1035	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1036	produces a constant value (for example through constant folding), you can
				1037	replace all uses of the instruction with the constant like this:</p>
				1038
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1039	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1040	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1041
				1042	</div>
				1043
				1044	<!-- ======================================================================= -->
				1045	<div class="doc_subsection">
				1046	<a name="User">The <tt>User</tt> class</a>
				1047	</div>
				1048
				1049	<div class="doc_text">
				1050
				1051	<p>
				1052	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1053	doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1054	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1055
				1056	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1057	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1058	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1059	referring to. The <tt>User</tt> class itself is a subclass of
				1060	<tt>Value</tt>.</p>
				1061
				1062	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1063	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1064	Single Assignment (SSA) form, there can only be one definition referred to,
				1065	allowing this direct connection. This connection provides the use-def
				1066	information in LLVM.</p>
				1067
				1068	</div>
				1069
				1070	<!-- _______________________________________________________________________ -->
				1071	<div class="doc_subsubsection">
				1072	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1073	</div>
				1074
				1075	<div class="doc_text">
				1076
				1077	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1078	an index access interface and through an iterator based interface.</p>
				1079
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1080	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1081	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1082	<tt>unsigned getNumOperands()</tt>
				1083	<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]	1084	convenient form for direct access.</p></li>
				1085
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1086	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1087	list<br>
				1088	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1089	Get an iterator to the start of the operand list.<br>
				1090	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1091	operand list.
				1092	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1093	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1094	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1095
				1096	</div>
				1097
				1098	<!-- ======================================================================= -->
				1099	<div class="doc_subsection">
				1100	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1101	</div>
				1102
				1103	<div class="doc_text">
				1104
				1105	<p><tt>#include "</tt><tt><a
				1106	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1107	doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1108	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1109	href="#Value"><tt>Value</tt></a></p>
				1110
				1111	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1112	instructions. It provides only a few methods, but is a very commonly used
				1113	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1114	opcode (instruction type) and the parent <a
				1115	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1116	into. To represent a specific type of instruction, one of many subclasses of
				1117	<tt>Instruction</tt> are used.</p>
				1118
				1119	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1120	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1121	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1122	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1123	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1124	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1125	file contains some meta-data about the various different types of instructions
				1126	in LLVM. It describes the enum values that are used as opcodes (for example
				1127	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1128	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1129	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1130	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1131	this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1132	<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1133
				1134	</div>
				1135
				1136	<!-- _______________________________________________________________________ -->
				1137	<div class="doc_subsubsection">
				1138	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1139	class</a>
				1140	</div>
				1141
				1142	<div class="doc_text">
				1143
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1144	<ul>
				1145	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1146	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1147	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1148	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1149	<p>Returns true if the instruction writes to memory, i.e. it is a
				1150	<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]	1151	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1152	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1153	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1154	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1155	in all ways to the original except that the instruction has no parent
				1156	(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]	1157	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1158	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1159
				1160	</div>
				1161
				1162	<!-- ======================================================================= -->
				1163	<div class="doc_subsection">
				1164	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1165	</div>
				1166
				1167	<div class="doc_text">
				1168
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1169	<p><tt>#include "<a
				1170	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1171	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1172	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1173	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1174
				1175	<p>This class represents a single entry multiple exit section of the code,
				1176	commonly known as a basic block by the compiler community. The
				1177	<tt>BasicBlock</tt> class maintains a list of <a
				1178	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1179	Matching the language definition, the last element of this list of instructions
				1180	is always a terminator instruction (a subclass of the <a
				1181	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1182
				1183	<p>In addition to tracking the list of instructions that make up the block, the
				1184	<tt>BasicBlock</tt> class also keeps track of the <a
				1185	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1186
				1187	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1188	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1189	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1190	<tt>label</tt>.</p>
				1191
				1192	</div>
				1193
				1194	<!-- _______________________________________________________________________ -->
				1195	<div class="doc_subsubsection">
				1196	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1197	class</a>
				1198	</div>
				1199
				1200	<div class="doc_text">
				1201
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1202	<ul>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1203
				1204	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1205	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1206
				1207	<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1208	insertion into a function. The constructor optionally takes a name for the new
				1209	block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
				1210	the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
				1211	automatically inserted at the end of the specified <a
				1212	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1213	manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
				1214
				1215	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1216	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1217	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1218	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt> -
				1219	STL-style functions for accessing the instruction list.
				1220
				1221	<p>These methods and typedefs are forwarding functions that have the same
				1222	semantics as the standard library methods of the same names. These methods
				1223	expose the underlying instruction list of a basic block in a way that is easy to
				1224	manipulate. To get the full complement of container operations (including
				1225	operations to update the list), you must use the <tt>getInstList()</tt>
				1226	method.</p></li>
				1227
				1228	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1229
				1230	<p>This method is used to get access to the underlying container that actually
				1231	holds the Instructions. This method must be used when there isn't a forwarding
				1232	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1233	to perform. Because there are no forwarding functions for "updating"
				1234	operations, you need to use this if you want to update the contents of a
				1235	<tt>BasicBlock</tt>.</p></li>
				1236
				1237	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1238
				1239	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1240	embedded into, or a null pointer if it is homeless.</p></li>
				1241
				1242	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1243
				1244	<p> Returns a pointer to the terminator instruction that appears at the end of
				1245	the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1246	instruction in the block is not a terminator, then a null pointer is
				1247	returned.</p></li>
				1248
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1249	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1250
				1251	</div>
				1252
				1253	<!-- ======================================================================= -->
				1254	<div class="doc_subsection">
				1255	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1256	</div>
				1257
				1258	<div class="doc_text">
				1259
				1260	<p><tt>#include "<a
				1261	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1262	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1263	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1264	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1265	href="#Value"><tt>Value</tt></a></p>
				1266
				1267	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1268	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1269	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1270	Because they are visible at global scope, they are also subject to linking with
				1271	other globals defined in different translation units. To control the linking
				1272	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1273	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1274	defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1275
				1276	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1277	<tt>static</tt> in C), it is not visible to code outside the current translation
				1278	unit, and does not participate in linking. If it has external linkage, it is
				1279	visible to external code, and does participate in linking. In addition to
				1280	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1281	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1282
				1283	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1284	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1285	global is always a pointer to its contents. It is important to remember this
				1286	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1287	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1288	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1289	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1290	the address of the first element of this array and the value of the
				1291	<tt>GlobalVariable</tt> are the same, they have different types. The
				1292	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1293	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1294	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1295	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1296	Language Reference Manual</a>.</p>
				1297
				1298	</div>
				1299
				1300	<!-- _______________________________________________________________________ -->
				1301	<div class="doc_subsubsection">
				1302	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1303	class</a>
				1304	</div>
				1305
				1306	<div class="doc_text">
				1307
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1308	<ul>
				1309	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1310	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1311	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1312	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1313	<p> </p>
				1314	</li>
				1315	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1316	<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]	1317	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1318	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1319
				1320	</div>
				1321
				1322	<!-- ======================================================================= -->
				1323	<div class="doc_subsection">
				1324	<a name="Function">The <tt>Function</tt> class</a>
				1325	</div>
				1326
				1327	<div class="doc_text">
				1328
				1329	<p><tt>#include "<a
				1330	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1331	info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
				1332	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1333	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1334
				1335	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1336	actually one of the more complex classes in the LLVM heirarchy because it must
				1337	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1338	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1339	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1340	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1341
				1342	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1343	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1344	ordering of the blocks in the function, which indicate how the code will be
				1345	layed out by the backend. Additionally, the first <a
				1346	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1347	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1348	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1349	nodes from a single <tt>Function</tt>. If the <a
				1350	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1351	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1352	function hasn't been linked in yet.</p>
				1353
				1354	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1355	<tt>Function</tt> class also keeps track of the list of formal <a
				1356	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1357	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1358	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1359	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1360
				1361	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1362	LLVM feature that is only used when you have to look up a value by name. Aside
				1363	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1364	internally to make sure that there are not conflicts between the names of <a
				1365	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1366	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1367	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1368
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1369	<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
				1370	and therefore also a <a href="#Constant">Constant</a>. The value of the function
				1371	is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1372	</div>
				1373
				1374	<!-- _______________________________________________________________________ -->
				1375	<div class="doc_subsubsection">
				1376	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1377	class</a>
				1378	</div>
				1379
				1380	<div class="doc_text">
				1381
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1382	<ul>
				1383	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1384	Ty, LinkageTypes Linkage, const std::string &N = "", Module Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1385
				1386	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1387	the the program. The constructor must specify the type of the function to
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1388	create and what type of linkage the function should have. The <a
				1389	href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1390	specifies the formal arguments and return value for the function. The same
				1391	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1392	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1393	in which the function is defined. If this argument is provided, the function
				1394	will automatically be inserted into that module's list of
				1395	functions.</p></li>
				1396
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1397	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1398
				1399	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1400	function is "external", it does not have a body, and thus must be resolved
				1401	by linking with a function defined in a different translation unit.</p></li>
				1402
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1403	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1404	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1405
				1406	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1407	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1408
				1409	<p>These are forwarding methods that make it easy to access the contents of
				1410	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1411	list.</p></li>
				1412
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1413	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1414
				1415	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1416	is necessary to use when you need to update the list or perform a complex
				1417	action that doesn't have a forwarding method.</p></li>
				1418
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1419	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1420	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1421	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1422
				1423	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1424	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1425
				1426	<p>These are forwarding methods that make it easy to access the contents of
				1427	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1428	list.</p></li>
				1429
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1430	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1431
				1432	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1433	necessary to use when you need to update the list or perform a complex
				1434	action that doesn't have a forwarding method.</p></li>
				1435
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1436	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1437
				1438	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1439	function. Because the entry block for the function is always the first
				1440	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1441
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1442	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1443	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1444
				1445	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1446	<tt>Function</tt> and returns the return type of the function, or the <a
				1447	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1448	function.</p></li>
				1449
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1450	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1451
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1452	<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]	1453	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1454	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1455
				1456	</div>
				1457
				1458	<!-- ======================================================================= -->
				1459	<div class="doc_subsection">
				1460	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1461	</div>
				1462
				1463	<div class="doc_text">
				1464
				1465	<p><tt>#include "<a
				1466	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1467	<br>
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1468	doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1469	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1470	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1471
				1472	<p>Global variables are represented with the (suprise suprise)
				1473	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1474	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1475	always referenced by their address (global values must live in memory, so their
				1476	"name" refers to their address). See <a
				1477	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1478	may have an initial value (which must be a <a
				1479	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1480	may be marked as "constant" themselves (indicating that their contents never
				1481	change at runtime).</p>
				1482
				1483	</div>
				1484
				1485	<!-- _______________________________________________________________________ -->
				1486	<div class="doc_subsubsection">
				1487	<a name="m_GlobalVariable">Important Public Members of the
				1488	<tt>GlobalVariable</tt> class</a>
				1489	</div>
				1490
				1491	<div class="doc_text">
				1492
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1493	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1494	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1495	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1496	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1497
				1498	<p>Create a new global variable of the specified type. If
				1499	<tt>isConstant</tt> is true then the global variable will be marked as
				1500	unchanging for the program. The Linkage parameter specifies the type of
				1501	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1502	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1503	the resultant global variable will have internal linkage. AppendingLinkage
				1504	concatenates together all instances (in different translation units) of the
				1505	variable into a single variable but is only applicable to arrays.  See
				1506	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1507	further details on linkage types. Optionally an initializer, a name, and the
				1508	module to put the variable into may be specified for the global variable as
				1509	well.</p></li>
				1510
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1511	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1512
				1513	<p>Returns true if this is a global variable that is known not to
				1514	be modified at runtime.</p></li>
				1515
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1516	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1517
				1518	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1519
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1520	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1521
				1522	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1523	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1524	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1525
				1526	</div>
				1527
				1528	<!-- ======================================================================= -->
				1529	<div class="doc_subsection">
				1530	<a name="Module">The <tt>Module</tt> class</a>
				1531	</div>
				1532
				1533	<div class="doc_text">
				1534
				1535	<p><tt>#include "<a
				1536	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1537	<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1538
				1539	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1540	programs. An LLVM module is effectively either a translation unit of the
				1541	original program or a combination of several translation units merged by the
				1542	linker. The <tt>Module</tt> class keeps track of a list of <a
				1543	href="#Function"><tt>Function</tt></a>s, a list of <a
				1544	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1545	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1546	helpful member functions that try to make common operations easy.</p>
				1547
				1548	</div>
				1549
				1550	<!-- _______________________________________________________________________ -->
				1551	<div class="doc_subsubsection">
				1552	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1553	</div>
				1554
				1555	<div class="doc_text">
				1556
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1557	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1558	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1559	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1560
				1561	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1562	provide a name for it (probably based on the name of the translation unit).</p>
				1563
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1564	<ul>
				1565	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1566	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1567
				1568	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1569	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1570
				1571	<p>These are forwarding methods that make it easy to access the contents of
				1572	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1573	list.</p></li>
				1574
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1575	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1576
				1577	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1578	necessary to use when you need to update the list or perform a complex
				1579	action that doesn't have a forwarding method.</p>
				1580
				1581	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1582	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1583
				1584	<hr>
				1585
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1586	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1587	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1588
				1589	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1590
				1591	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1592	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1593
				1594	<p> These are forwarding methods that make it easy to access the contents of
				1595	a <tt>Module</tt> object's <a
				1596	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1597
				1598	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1599
				1600	<p>Returns the list of <a
				1601	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1602	use when you need to update the list or perform a complex action that
				1603	doesn't have a forwarding method.</p>
				1604
				1605	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1606	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1607
				1608	<hr>
				1609
				1610	<ul>
				1611	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1612
				1613	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1614	for this <tt>Module</tt>.</p>
				1615
				1616	<p><!-- Convenience methods --></p></li>
				1617	</ul>
				1618
				1619	<hr>
				1620
				1621	<ul>
				1622	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1623	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1624
				1625	<p>Look up the specified function in the <tt>Module</tt> <a
				1626	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1627	<tt>null</tt>.</p></li>
				1628
				1629	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1630	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1631
				1632	<p>Look up the specified function in the <tt>Module</tt> <a
				1633	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1634	external declaration for the function and return it.</p></li>
				1635
				1636	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1637
				1638	<p>If there is at least one entry in the <a
				1639	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1640	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1641	string.</p></li>
				1642
				1643	<li><tt>bool addTypeName(const std::string &Name, const <a
				1644	href="#Type">Type</a> *Ty)</tt>
				1645
				1646	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1647	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1648	name, true is returned and the <a
				1649	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1650	</ul>
				1651
				1652	</div>
				1653
				1654	<!-- ======================================================================= -->
				1655	<div class="doc_subsection">
				1656	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1657	</div>
				1658
				1659	<div class="doc_text">
				1660
				1661	<p>Constant represents a base class for different types of constants. It
				1662	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1663	ConstantArray etc for representing the various types of Constants.</p>
				1664
				1665	</div>
				1666
				1667	<!-- _______________________________________________________________________ -->
				1668	<div class="doc_subsubsection">
				1669	<a name="m_Value">Important Public Methods</a>
				1670	</div>
				1671
				1672	<div class="doc_text">
				1673
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1674	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1675	<hr> Important Subclasses of Constant
				1676	<p> </p>
				1677	<ul>
				1678	<li>ConstantSInt : This subclass of Constant represents a signed
				1679	integer constant.
				1680	<ul>
				1681	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1682	this constant. </li>
				1683	</ul>
				1684	</li>
				1685	<li>ConstantUInt : This class represents an unsigned integer.
				1686	<ul>
				1687	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value
				1688	of this constant. </li>
				1689	</ul>
				1690	</li>
				1691	<li>ConstantFP : This class represents a floating point constant.
				1692	<ul>
				1693	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1694	this constant. </li>
				1695	</ul>
				1696	</li>
				1697	<li>ConstantBool : This represents a boolean constant.
				1698	<ul>
				1699	<li><tt>bool getValue() const</tt>: Returns the underlying value of
				1700	this constant. </li>
				1701	</ul>
				1702	</li>
				1703	<li>ConstantArray : This represents a constant array.
				1704	<ul>
				1705	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1706	Returns a Vecotr of component constants that makeup this array. </li>
				1707	</ul>
				1708	</li>
				1709	<li>ConstantStruct : This represents a constant struct.
				1710	<ul>
				1711	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1712	Returns a Vecotr of component constants that makeup this array. </li>
				1713	</ul>
				1714	</li>
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1715	<li>GlobalValue : This represents either a global variable or a
				1716	function. In either case, the value is a constant fixed address
				1717	(after linking).
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1718	</li>
				1719	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1720	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1721	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1722	</div>
				1723
				1724	<!-- ======================================================================= -->
				1725	<div class="doc_subsection">
				1726	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1727	</div>
				1728
				1729	<div class="doc_text">
				1730
				1731	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1732	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1733	types are instances of subclasses of type like FunctionType, ArrayType
				1734	etc. DerivedType is the interface for all such dervied types including
				1735	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1736	be recursive (StructType). There exists exactly one instance of any type
				1737	structure at a time. This allows using pointer equality of Type *s for comparing
				1738	types.</p>
				1739
				1740	</div>
				1741
				1742	<!-- _______________________________________________________________________ -->
				1743	<div class="doc_subsubsection">
				1744	<a name="m_Value">Important Public Methods</a>
				1745	</div>
				1746
				1747	<div class="doc_text">
				1748
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1749	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1750
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1751	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1752	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1753	not true for Float and Double. </li>
				1754
				1755	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1756	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1757	return false as they do with isSigned. This returns true for UByteTy,
				1758	UShortTy, UIntTy, and ULongTy. </li>
				1759
Chris Lattner	4573f1b	2004-07-08 17:49:37 +0000	[diff] [blame]	1760	<li><tt>bool isInteger() const</tt>: Equivalent to isSigned() \|\| isUnsigned().</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1761
				1762	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1763	type, which is either Bool type or one of the Integer types.</li>
				1764
				1765	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1766	floating point types.</li>
				1767
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1768	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1769	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]	1770	example, uint to int or one pointer type to another.</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1771
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1772	<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1773	<p>Derived Types</p>
				1774
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1775	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1776	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1777	<ul>
				1778	<li><tt>const Type * getElementType() const</tt>: Returns the type of
				1779	each of the elements in the sequential type. </li>
				1780	</ul>
				1781	</li>
				1782	<li>ArrayType : This is a subclass of SequentialType and defines
				1783	interface for array types.
				1784	<ul>
				1785	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1786	elements in the array. </li>
				1787	</ul>
				1788	</li>
				1789	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1790	<li>StructType : subclass of DerivedTypes for struct types </li>
				1791	<li>FunctionType : subclass of DerivedTypes for function types.
				1792	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1793	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1794	function</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1795	<li><tt> const Type * getReturnType() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1796	return type of the function.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1797	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1798	the type of the ith parameter.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1799	<li><tt> const unsigned getNumParams() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1800	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1801	</ul>
				1802	</li>
				1803	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1804	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1805	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1806
				1807	</div>
				1808
				1809	<!-- ======================================================================= -->
				1810	<div class="doc_subsection">
				1811	<a name="Argument">The <tt>Argument</tt> class</a>
				1812	</div>
				1813
				1814	<div class="doc_text">
				1815
				1816	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1817	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1818	arguments. An argument has a pointer to the parent Function.</p>
				1819
				1820	</div>
				1821
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1822	<!-- ======================================================================= -->
				1823	<div class="doc_subsection">
				1824	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1825	</div>
				1826	<div class="doc_text">
				1827	<p>This class provides a symbol table that the
				1828	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1829	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1830	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1831	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1832	type. It hides the data it contains and provides access to it through a
				1833	controlled interface.</p>
				1834
				1835	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1836	structure of the information it holds. The class contains two
				1837	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1838	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1839	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1840	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1841	however, are stored in a single dimension and accessed only by name.</p>
				1842
				1843	<p>The interface of this class provides three basic types of operations:
				1844	<ol>
				1845	<li><em>Accessors</em>. Accessors provide read-only access to information
				1846	such as finding a value for a name with the
				1847	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1848	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1849	<tt>SymbolTable</tt> with methods like
				1850	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1851	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1852	of the symbol table in well defined ways, such as the method
				1853	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1854	</ol>
				1855
				1856	<h3>Accessors</h3>
				1857	<dl>
				1858	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1859	</dt>
				1860	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1861	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1862	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1863
				1864	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1865	<dd>The <tt>lookupType</tt> method searches through the types for a
				1866	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1867	is not found, null is returned.</dd>
				1868
				1869	<dt><tt>bool hasTypes() const</tt>:</dt>
				1870	<dd>This function returns true if an entry has been made into the type
				1871	map.</dd>
				1872
				1873	<dt><tt>bool isEmpty() const</tt>:</dt>
				1874	<dd>This function returns true if both the value and types maps are
				1875	empty</dd>
				1876
				1877	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1878	<dd>This function returns the name of the Value provided or the empty
				1879	string if the Value is not in the symbol table.</dd>
				1880
				1881	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1882	<dd>This function returns the name of the Type provided or the empty
				1883	string if the Type is not in the symbol table.</dd>
				1884	</dl>
				1885
				1886	<h3>Mutators</h3>
				1887	<dl>
				1888	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1889	<dd>This method adds the provided value to the symbol table. The Value must
				1890	have both a name and a type which are extracted and used to place the value
				1891	in the correct type plane under the value's name.</dd>
				1892
				1893	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1894	<dd> Inserts a constant or type into the symbol table with the specified
				1895	name. There can be a many to one mapping between names and constants
				1896	or types.</dd>
				1897
				1898	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1899	<dd> Inserts a type into the symbol table with the specified name. There
				1900	can be a many-to-one mapping between names and types. This method
				1901	allows a type with an existing entry in the symbol table to get
				1902	a new name.</dd>
				1903
				1904	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1905	<dd> This method removes a named value from the symbol table. The
				1906	type and name of the Value are extracted from \p N and used to
				1907	lookup the Value in the correct type plane. If the Value is
				1908	not in the symbol table, this method silently ignores the
				1909	request.</dd>
				1910
				1911	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1912	<dd> This method removes a named type from the symbol table. The
				1913	name of the type is extracted from \P T and used to look up
				1914	the Type in the type map. If the Type is not in the symbol
				1915	table, this method silently ignores the request.</dd>
				1916
				1917	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1918	<dd> Remove a constant or type with the specified name from the
				1919	symbol table.</dd>
				1920
				1921	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1922	<dd> Remove a type with the specified name from the symbol table.
				1923	Returns the removed Type.</dd>
				1924
				1925	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1926	<dd> Removes a specific value from the symbol table.
				1927	Returns the removed value.</dd>
				1928
				1929	<dt><tt>bool strip()</tt>:</dt>
				1930	<dd> This method will strip the symbol table of its names leaving
				1931	the type and values. </dd>
				1932
				1933	<dt><tt>void clear()</tt>:</dt>
				1934	<dd>Empty the symbol table completely.</dd>
				1935	</dl>
				1936
				1937	<h3>Iteration</h3>
				1938	<p>The following functions describe three types of iterators you can obtain
				1939	the beginning or end of the sequence for both const and non-const. It is
				1940	important to keep track of the different kinds of iterators. There are
				1941	three idioms worth pointing out:</p>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1942	<table>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1943	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1944	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1945	<td align="left">Planes Of name/Value maps</td><td>PI</td>
				1946	<td align="left"><tt><pre>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1947	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1948	PE = ST.plane_end(); PI != PE; ++PI ) {
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1949	PI->first // This is the Type* of the plane
				1950	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1951	</pre></tt></td>
				1952	</tr>
				1953	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1954	<td align="left">All name/Type Pairs</td><td>TI</td>
				1955	<td align="left"><tt><pre>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1956	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1957	TE = ST.type_end(); TI != TE; ++TI )
				1958	TI->first // This is the name of the type
				1959	TI->second // This is the Type* value associated with the name
				1960	</pre></tt></td>
				1961	</tr>
				1962	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1963	<td align="left">name/Value pairs in a plane</td><td>VI</td>
				1964	<td align="left"><tt><pre>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1965	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1966	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1967	VI->first // This is the name of the Value
				1968	VI->second // This is the Value* value associated with the name
				1969	</pre></tt></td>
				1970	</tr>
				1971	</table>
				1972	<p>Using the recommended iterator names and idioms will help you avoid
				1973	making mistakes. Of particular note, make sure that whenever you use
				1974	value_begin(SomeType) that you always compare the resulting iterator
				1975	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1976	will loop infinitely.</p>
				1977
				1978	<dl>
				1979
				1980	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1981	<dd>Get an iterator that starts at the beginning of the type planes.
				1982	The iterator will iterate over the Type/ValueMap pairs in the
				1983	type planes. </dd>
				1984
				1985	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1986	<dd>Get a const_iterator that starts at the beginning of the type
				1987	planes. The iterator will iterate over the Type/ValueMap pairs
				1988	in the type planes. </dd>
				1989
				1990	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1991	<dd>Get an iterator at the end of the type planes. This serves as
				1992	the marker for end of iteration over the type planes.</dd>
				1993
				1994	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				1995	<dd>Get a const_iterator at the end of the type planes. This serves as
				1996	the marker for end of iteration over the type planes.</dd>
				1997
				1998	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1999	<dd>Get an iterator that starts at the beginning of a type plane.
				2000	The iterator will iterate over the name/value pairs in the type plane.
				2001	Note: The type plane must already exist before using this.</dd>
				2002
				2003	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				2004	<dd>Get a const_iterator that starts at the beginning of a type plane.
				2005	The iterator will iterate over the name/value pairs in the type plane.
				2006	Note: The type plane must already exist before using this.</dd>
				2007
				2008	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				2009	<dd>Get an iterator to the end of a type plane. This serves as the marker
				2010	for end of iteration of the type plane.
				2011	Note: The type plane must already exist before using this.</dd>
				2012
				2013	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				2014	<dd>Get a const_iterator to the end of a type plane. This serves as the
				2015	marker for end of iteration of the type plane.
				2016	Note: the type plane must already exist before using this.</dd>
				2017
				2018	<dt><tt>type_iterator type_begin()</tt>:</dt>
				2019	<dd>Get an iterator to the start of the name/Type map.</dd>
				2020
				2021	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				2022	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				2023
				2024	<dt><tt>type_iterator type_end()</tt>:</dt>
				2025	<dd>Get an iterator to the end of the name/Type map. This serves as the
				2026	marker for end of iteration of the types.</dd>
				2027
				2028	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2029	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2030	as the marker for end of iteration of the types.</dd>
				2031
				2032	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2033	<dd>This method returns a plane_const_iterator for iteration over
				2034	the type planes starting at a specific plane, given by \p Ty.</dd>
				2035
				2036	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2037	<dd>This method returns a plane_iterator for iteration over the
				2038	type planes starting at a specific plane, given by \p Ty.</dd>
				2039
				2040	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2041	<dd>This method returns a ValueMap* for a specific type plane. This
				2042	interface is deprecated and may go away in the future.</dd>
				2043	</dl>
				2044	</div>
				2045
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2046	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2047	<hr>
				2048	<address>
				2049	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2050	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2051	<a href="http://validator.w3.org/check/referer"><img
				2052	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2053
				2054	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2055	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2056	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2057	Last modified: $Date$
				2058	</address>
				2059
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2060	</body>
				2061	</html>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	2062	<!-- vim: sw=2 noai
				2063	-->