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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
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Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	8	<body>
				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
				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>
				92	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				93	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	94	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				95	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				96	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class
				97	</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	98	</ul></li>
				99	<li><a href="#Module">The <tt>Module</tt> class</a></li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	100	<li><a href="#Constant">The <tt>Constant</tt> class</a></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	101	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	102	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
				103	</ul></li>
				104	</ul></li>
				105	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				106	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				107	<ul>
				108	<li>Creating, inserting, moving and deleting from LLVM lists </li>
				109	</ul>
				110	</li>
				111	<li>Important iterator invalidation semantics to be aware of.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	112	</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	113	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	114
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	115	<div class="doc_author">
				116	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner	94c4359	2004-05-26 16:52:55 +0000	[diff] [blame]	117	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
				118	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
				119	<a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	120	</div>
				121
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	122	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	123	<div class="doc_section">
				124	<a name="introduction">Introduction </a>
				125	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	126	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	127
				128	<div class="doc_text">
				129
				130	<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]	131	interfaces available in the LLVM source-base. This manual is not
				132	intended to explain what LLVM is, how it works, and what LLVM code looks
				133	like. It assumes that you know the basics of LLVM and are interested
				134	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	135	code.</p>
				136
				137	<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]	138	way in the continuously growing source code that makes up the LLVM
				139	infrastructure. Note that this manual is not intended to serve as a
				140	replacement for reading the source code, so if you think there should be
				141	a method in one of these classes to do something, but it's not listed,
				142	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				143	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	144
				145	<p>The first section of this document describes general information that is
				146	useful to know when working in the LLVM infrastructure, and the second describes
				147	the Core LLVM classes. In the future this manual will be extended with
				148	information describing how to use extension libraries, such as dominator
				149	information, CFG traversal routines, and useful utilities like the <tt><a
				150	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				151
				152	</div>
				153
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	154	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	155	<div class="doc_section">
				156	<a name="general">General Information</a>
				157	</div>
				158	<!-- *********************************************************************** -->
				159
				160	<div class="doc_text">
				161
				162	<p>This section contains general information that is useful if you are working
				163	in the LLVM source-base, but that isn't specific to any particular API.</p>
				164
				165	</div>
				166
				167	<!-- ======================================================================= -->
				168	<div class="doc_subsection">
				169	<a name="stl">The C++ Standard Template Library</a>
				170	</div>
				171
				172	<div class="doc_text">
				173
				174	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	175	perhaps much more than you are used to, or have seen before. Because of
				176	this, you might want to do a little background reading in the
				177	techniques used and capabilities of the library. There are many good
				178	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]	179	can get, so it will not be discussed in this document.</p>
				180
				181	<p>Here are some useful links:</p>
				182
				183	<ol>
				184
				185	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				186	reference</a> - an excellent reference for the STL and other parts of the
				187	standard C++ library.</li>
				188
				189	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
				190	O'Reilly book in the making. It has a decent <a
				191	href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
				192	Reference</a> that rivals Dinkumware's, and is actually free until the book is
				193	published.</li>
				194
				195	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				196	Questions</a></li>
				197
				198	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				199	Contains a useful <a
				200	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				201	STL</a>.</li>
				202
				203	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				204	Page</a></li>
				205
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	206	<li><a href="http://www.linux.com.cn/Bruce_Eckel/TICPPv2/Contents.htm">
				207	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				208	the book).</a></li>
				209
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	210	</ol>
				211
				212	<p>You are also encouraged to take a look at the <a
				213	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				214	to write maintainable code more than where to put your curly braces.</p>
				215
				216	</div>
				217
				218	<!-- ======================================================================= -->
				219	<div class="doc_subsection">
				220	<a name="stl">Other useful references</a>
				221	</div>
				222
				223	<div class="doc_text">
				224
				225	<p>LLVM is currently using CVS as its source versioning system. You may find
				226	this reference handy:</p>
				227
				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	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	231	</ol>
				232
				233	</div>
				234
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	235	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	236	<div class="doc_section">
				237	<a name="apis">Important and useful LLVM APIs</a>
				238	</div>
				239	<!-- *********************************************************************** -->
				240
				241	<div class="doc_text">
				242
				243	<p>Here we highlight some LLVM APIs that are generally useful and good to
				244	know about when writing transformations.</p>
				245
				246	</div>
				247
				248	<!-- ======================================================================= -->
				249	<div class="doc_subsection">
				250	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				251	</div>
				252
				253	<div class="doc_text">
				254
				255	<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]	256	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				257	operator, but they don't have some drawbacks (primarily stemming from
				258	the fact that <tt>dynamic_cast<></tt> only works on classes that
				259	have a v-table). Because they are used so often, you must know what they
				260	do and how they work. All of these templates are defined in the <a
				261	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	262	file (note that you very rarely have to include this file directly).</p>
				263
				264	<dl>
				265	<dt><tt>isa<></tt>: </dt>
				266
				267	<dd>The <tt>isa<></tt> operator works exactly like the Java
				268	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				269	a reference or pointer points to an instance of the specified class. This can
				270	be very useful for constraint checking of various sorts (example below).</dd>
				271
				272	<dt><tt>cast<></tt>: </dt>
				273
				274	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				275	converts a pointer or reference from a base class to a derived cast, causing
				276	an assertion failure if it is not really an instance of the right type. This
				277	should be used in cases where you have some information that makes you believe
				278	that something is of the right type. An example of the <tt>isa<></tt>
				279	and <tt>cast<></tt> template is:
				280
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	281	<pre>
				282	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				283	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				284	return true;
				285
				286	<i>// Otherwise, it must be an instruction...</i>
				287	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				288	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	289
				290	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				291	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				292	operator.</p>
				293
				294	</dd>
				295
				296	<dt><tt>dyn_cast<></tt>:</dt>
				297
				298	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				299	checks to see if the operand is of the specified type, and if so, returns a
				300	pointer to it (this operator does not work with references). If the operand is
				301	not of the correct type, a null pointer is returned. Thus, this works very
				302	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				303	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				304	in an <tt>if</tt> statement or some other flow control statement like this:
				305
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	306	<pre>
				307	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				308	...
				309	}
				310	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	311
				312	<p> This form of the <tt>if</tt> statement effectively combines together a
				313	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				314	statement, which is very convenient.</p>
				315
				316	<p> Another common example is:</p>
				317
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	318	<pre>
				319	<i>// Loop over all of the phi nodes in a basic block</i>
				320	BasicBlock::iterator BBI = BB->begin();
				321	for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(BBI); ++BBI)
				322	std::cerr << *PN;
				323	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	324
				325	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				326	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				327	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				328	check for lots of different variants of classes. If you find yourself
				329	wanting to do this, it is much cleaner and more efficient to use the
				330	InstVisitor class to dispatch over the instruction type directly.</p>
				331
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	332	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	333
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	334	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	335
				336	<dd>The <tt>cast_or_null<></tt> operator works just like the
				337	<tt>cast<></tt> operator, except that it allows for a null pointer as
				338	an argument (which it then propagates). This can sometimes be useful,
				339	allowing you to combine several null checks into one.</dd>
				340
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	341	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	342
				343	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				344	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				345	as an argument (which it then propagates). This can sometimes be useful,
				346	allowing you to combine several null checks into one.</dd>
				347
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	348	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	349
				350	<p>These five templates can be used with any classes, whether they have a
				351	v-table or not. To add support for these templates, you simply need to add
				352	<tt>classof</tt> static methods to the class you are interested casting
				353	to. Describing this is currently outside the scope of this document, but there
				354	are lots of examples in the LLVM source base.</p>
				355
				356	</div>
				357
				358	<!-- ======================================================================= -->
				359	<div class="doc_subsection">
				360	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				361	</div>
				362
				363	<div class="doc_text">
				364
				365	<p>Often when working on your pass you will put a bunch of debugging printouts
				366	and other code into your pass. After you get it working, you want to remove
				367	it... but you may need it again in the future (to work out new bugs that you run
				368	across).</p>
				369
				370	<p> Naturally, because of this, you don't want to delete the debug printouts,
				371	but you don't want them to always be noisy. A standard compromise is to comment
				372	them out, allowing you to enable them if you need them in the future.</p>
				373
				374	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				375	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				376	this problem. Basically, you can put arbitrary code into the argument of the
				377	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				378	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				379
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	380	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	381
				382	<p>Then you can run your pass like this:</p>
				383
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	384	<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]	385
				386	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				387	to not have to create "yet another" command line option for the debug output for
				388	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				389	so they do not cause a performance impact at all (for the same reason, they
				390	should also not contain side-effects!).</p>
				391
				392	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				393	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				394	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				395	program hasn't been started yet, you can always just run it with
				396	<tt>-debug</tt>.</p>
				397
				398	</div>
				399
				400	<!-- _______________________________________________________________________ -->
				401	<div class="doc_subsubsection">
				402	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				403	the <tt>-debug-only</tt> option</a>
				404	</div>
				405
				406	<div class="doc_text">
				407
				408	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				409	just turns on <b>too much</b> information (such as when working on the code
				410	generator). If you want to enable debug information with more fine-grained
				411	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				412	option as follows:</p>
				413
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	414	<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]	415
				416	<p>Then you can run your pass like this:</p>
				417
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	418	<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]	419
				420	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				421	a file, to specify the debug type for the entire module (if you do this before
				422	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				423	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				424	"bar", because there is no system in place to ensure that names do not
				425	conflict. If two different modules use the same string, they will all be turned
				426	on when the name is specified. This allows, for example, all debug information
				427	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	428	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	429
				430	</div>
				431
				432	<!-- ======================================================================= -->
				433	<div class="doc_subsection">
				434	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				435	option</a>
				436	</div>
				437
				438	<div class="doc_text">
				439
				440	<p>The "<tt><a
				441	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				442	provides a template named <tt>Statistic</tt> that is used as a unified way to
				443	keep track of what the LLVM compiler is doing and how effective various
				444	optimizations are. It is useful to see what optimizations are contributing to
				445	making a particular program run faster.</p>
				446
				447	<p>Often you may run your pass on some big program, and you're interested to see
				448	how many times it makes a certain transformation. Although you can do this with
				449	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				450	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				451	keep track of this information, and the calculated information is presented in a
				452	uniform manner with the rest of the passes being executed.</p>
				453
				454	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				455	it are as follows:</p>
				456
				457	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	458	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	459	<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]	460
				461	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				462	but if you do not specify a template argument, it defaults to acting like
				463	an unsigned int counter (this is usually what you want).</p></li>
				464
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	465	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	466	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	467	</li>
				468	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	469
				470	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				471	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				472
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	473	<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]	474
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	475	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				476	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	477
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	478	<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]	479
				480	<p>Obviously, with so many optimizations, having a unified framework for this
				481	stuff is very nice. Making your pass fit well into the framework makes it more
				482	maintainable and useful.</p>
				483
				484	</div>
				485
				486	<!-- *********************************************************************** -->
				487	<div class="doc_section">
				488	<a name="common">Helpful Hints for Common Operations</a>
				489	</div>
				490	<!-- *********************************************************************** -->
				491
				492	<div class="doc_text">
				493
				494	<p>This section describes how to perform some very simple transformations of
				495	LLVM code. This is meant to give examples of common idioms used, showing the
				496	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				497	you should also read about the main classes that you will be working with. The
				498	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				499	and descriptions of the main classes that you should know about.</p>
				500
				501	</div>
				502
				503	<!-- NOTE: this section should be heavy on example code -->
				504	<!-- ======================================================================= -->
				505	<div class="doc_subsection">
				506	<a name="inspection">Basic Inspection and Traversal Routines</a>
				507	</div>
				508
				509	<div class="doc_text">
				510
				511	<p>The LLVM compiler infrastructure have many different data structures that may
				512	be traversed. Following the example of the C++ standard template library, the
				513	techniques used to traverse these various data structures are all basically the
				514	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				515	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				516	function returns an iterator pointing to one past the last valid element of the
				517	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				518	between the two operations.</p>
				519
				520	<p>Because the pattern for iteration is common across many different aspects of
				521	the program representation, the standard template library algorithms may be used
				522	on them, and it is easier to remember how to iterate. First we show a few common
				523	examples of the data structures that need to be traversed. Other data
				524	structures are traversed in very similar ways.</p>
				525
				526	</div>
				527
				528	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	529	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	530	<a name="iterate_function">Iterating over the </a><a
				531	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				532	href="#Function"><tt>Function</tt></a>
				533	</div>
				534
				535	<div class="doc_text">
				536
				537	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				538	transform in some way; in particular, you'd like to manipulate its
				539	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				540	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				541	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				542	<tt>Instruction</tt>s it contains:</p>
				543
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	544	<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]	545
				546	<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]	547	invoking member functions of the <tt>Instruction</tt> class. This is
				548	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	549	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	550	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				551
				552	</div>
				553
				554	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	555	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	556	<a name="iterate_basicblock">Iterating over the </a><a
				557	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				558	href="#BasicBlock"><tt>BasicBlock</tt></a>
				559	</div>
				560
				561	<div class="doc_text">
				562
				563	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				564	easy to iterate over the individual instructions that make up
				565	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				566	a <tt>BasicBlock</tt>:</p>
				567
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	568	<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]	569
				570	<p>However, this isn't really the best way to print out the contents of a
				571	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				572	anything you'll care about, you could have just invoked the print routine on the
				573	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				574
				575	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				576	it will print out the contents of the pointer, instead of the pointer value you
				577	might expect. This is a deprecated interface that will be removed in the
				578	future, so it's best not to depend on it. To print out the pointer value for
				579	now, you must cast to <tt>void*</tt>.</p>
				580
				581	</div>
				582
				583	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	584	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	585	<a name="iterate_institer">Iterating over the </a><a
				586	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				587	href="#Function"><tt>Function</tt></a>
				588	</div>
				589
				590	<div class="doc_text">
				591
				592	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				593	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				594	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				595	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				596	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]	597	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]	598
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	599	<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]	600	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				601	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	602	initialize a worklist to contain all instructions in a <tt>Function</tt>
				603	F, all you would need to do is something like:
				604	<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]	605
				606	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				607	<tt>Function</tt> pointed to by F.</p>
				608
				609	</div>
				610
				611	<!-- _______________________________________________________________________ -->
				612	<div class="doc_subsubsection">
				613	<a name="iterate_convert">Turning an iterator into a class pointer (and
				614	vice-versa)</a>
				615	</div>
				616
				617	<div class="doc_text">
				618
				619	<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]	620	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]	621	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	622	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]	623	is a <tt>BasicBlock::const_iterator</tt>:</p>
				624
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	625	<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]	626
				627	<p>However, the iterators you'll be working with in the LLVM framework are
				628	special: they will automatically convert to a ptr-to-instance type whenever they
				629	need to. Instead of dereferencing the iterator and then taking the address of
				630	the result, you can simply assign the iterator to the proper pointer type and
				631	you get the dereference and address-of operation as a result of the assignment
				632	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				633	the last line of the last example,</p>
				634
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	635	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	636
				637	<p>is semantically equivalent to</p>
				638
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	639	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	640
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	641	<p>It's also possible to turn a class pointer into the corresponding iterator,
				642	and this is a constant time operation (very efficient). The following code
				643	snippet illustrates use of the conversion constructors provided by LLVM
				644	iterators. By using these, you can explicitly grab the iterator of something
				645	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	646
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	647	<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]	648
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	649	</div>
				650
				651	<!--_______________________________________________________________________-->
				652	<div class="doc_subsubsection">
				653	<a name="iterate_complex">Finding call sites: a slightly more complex
				654	example</a>
				655	</div>
				656
				657	<div class="doc_text">
				658
				659	<p>Say that you're writing a FunctionPass and would like to count all the
				660	locations in the entire module (that is, across every <tt>Function</tt>) where a
				661	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				662	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]	663	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]	664	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				665	is what we want to do:</p>
				666
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	667	<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]	668
				669	<p>And the actual code is (remember, since we're writing a
				670	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				671	override the <tt>runOnFunction</tt> method...):</p>
				672
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	673	<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
				674	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				675	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]	676
				677	</div>
				678
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	679	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	680	<div class="doc_subsubsection">
				681	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				682	</div>
				683
				684	<div class="doc_text">
				685
				686	<p>You may have noticed that the previous example was a bit oversimplified in
				687	that it did not deal with call sites generated by 'invoke' instructions. In
				688	this, and in other situations, you may find that you want to treat
				689	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				690	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				691	less closely-related things. For these cases, LLVM provides a handy wrapper
				692	class called <a
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	693	href="http://llvm.cs.uiuc.edu/doxygen/classCallSite.html"><tt>CallSite</tt></a>.
				694	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				695	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	696	<tt>InvokeInst</tt>s.</p>
				697
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	698	<p>This class has "value semantics": it should be passed by value, not by
				699	reference and it should not be dynamically allocated or deallocated using
				700	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				701	assignable and constructable, with costs equivalents to that of a bare pointer.
				702	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]	703
				704	</div>
				705
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	706	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	707	<div class="doc_subsubsection">
				708	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				709	</div>
				710
				711	<div class="doc_text">
				712
				713	<p>Frequently, we might have an instance of the <a
				714	href="/doxygen/classValue.html">Value Class</a> and we want to determine which
				715	<tt>User</tt>s use the <tt>Value</tt>. The list of all <tt>User</tt>s of a
				716	particular <tt>Value</tt> is called a <i>def-use</i> chain. For example, let's
				717	say we have a <tt>Function*</tt> named <tt>F</tt> to a particular function
				718	<tt>foo</tt>. Finding all of the instructions that <i>use</i> <tt>foo</tt> is as
				719	simple as iterating over the <i>def-use</i> chain of <tt>F</tt>:</p>
				720
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	721	<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]	722
				723	<p>Alternately, it's common to have an instance of the <a
				724	href="/doxygen/classUser.html">User Class</a> and need to know what
				725	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				726	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				727	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				728	all of the values that a particular instruction uses (that is, the operands of
				729	the particular <tt>Instruction</tt>):</p>
				730
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	731	<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]	732
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	733	<!--
				734	def-use chains ("finding all users of"): Value::use_begin/use_end
				735	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]	736	-->
				737
				738	</div>
				739
				740	<!-- ======================================================================= -->
				741	<div class="doc_subsection">
				742	<a name="simplechanges">Making simple changes</a>
				743	</div>
				744
				745	<div class="doc_text">
				746
				747	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	748	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	749	transformations, it's fairly common to manipulate the contents of basic
				750	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	751	and gives example code.</p>
				752
				753	</div>
				754
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	755	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	756	<div class="doc_subsubsection">
				757	<a name="schanges_creating">Creating and inserting new
				758	<tt>Instruction</tt>s</a>
				759	</div>
				760
				761	<div class="doc_text">
				762
				763	<p><i>Instantiating Instructions</i></p>
				764
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	765	<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]	766	constructor for the kind of instruction to instantiate and provide the necessary
				767	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				768	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				769
				770	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				771
				772	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				773	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				774	subclass is likely to have varying default parameters which change the semantics
				775	of the instruction, so refer to the <a
				776	href="/doxygen/classInstruction.html">doxygen documentation for the subclass of
				777	Instruction</a> that you're interested in instantiating.</p>
				778
				779	<p><i>Naming values</i></p>
				780
				781	<p>It is very useful to name the values of instructions when you're able to, as
				782	this facilitates the debugging of your transformations. If you end up looking
				783	at generated LLVM machine code, you definitely want to have logical names
				784	associated with the results of instructions! By supplying a value for the
				785	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				786	associate a logical name with the result of the instruction's execution at
				787	runtime. For example, say that I'm writing a transformation that dynamically
				788	allocates space for an integer on the stack, and that integer is going to be
				789	used as some kind of index by some other code. To accomplish this, I place an
				790	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				791	<tt>Function</tt>, and I'm intending to use it within the same
				792	<tt>Function</tt>. I might do:</p>
				793
				794	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				795
				796	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				797	execution value, which is a pointer to an integer on the runtime stack.</p>
				798
				799	<p><i>Inserting instructions</i></p>
				800
				801	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				802	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				803
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	804	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	805	<li>Insertion into an explicit instruction list
				806
				807	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				808	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				809	before <tt>*pi</tt>, we do the following: </p>
				810
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	811	<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>
				812
				813	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				814	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				815	classes provide constructors which take a pointer to a
				816	<tt>BasicBlock</tt> to be appended to. For example code that
				817	looked like: </p>
				818
				819	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				820
				821	<p>becomes: </p>
				822
				823	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				824
				825	<p>which is much cleaner, especially if you are creating
				826	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	827
				828	<li>Insertion into an implicit instruction list
				829
				830	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				831	are implicitly associated with an existing instruction list: the instruction
				832	list of the enclosing basic block. Thus, we could have accomplished the same
				833	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				834	</p>
				835
				836	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				837
				838	<p>In fact, this sequence of steps occurs so frequently that the
				839	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				840	constructors which take (as a default parameter) a pointer to an
				841	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				842	precede. That is, <tt>Instruction</tt> constructors are capable of
				843	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				844	provided instruction, immediately before that instruction. Using an
				845	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				846	parameter, the above code becomes:</p>
				847
				848	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				849
				850	<p>which is much cleaner, especially if you're creating a lot of
				851	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				852	</ul>
				853
				854	</div>
				855
				856	<!--_______________________________________________________________________-->
				857	<div class="doc_subsubsection">
				858	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				859	</div>
				860
				861	<div class="doc_text">
				862
				863	<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]	864	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	865	you must have a pointer to the instruction that you wish to delete. Second, you
				866	need to obtain the pointer to that instruction's basic block. You use the
				867	pointer to the basic block to get its list of instructions and then use the
				868	erase function to remove your instruction. For example:</p>
				869
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	870	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				871	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]	872
				873	</div>
				874
				875	<!--_______________________________________________________________________-->
				876	<div class="doc_subsubsection">
				877	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				878	<tt>Value</tt></a>
				879	</div>
				880
				881	<div class="doc_text">
				882
				883	<p><i>Replacing individual instructions</i></p>
				884
				885	<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]	886	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	887	and <tt>ReplaceInstWithInst</tt>.</p>
				888
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	889	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	890
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	891	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	892	<li><tt>ReplaceInstWithValue</tt>
				893
				894	<p>This function replaces all uses (within a basic block) of a given
				895	instruction with a value, and then removes the original instruction. The
				896	following example illustrates the replacement of the result of a particular
				897	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				898	pointer to an integer.</p>
				899
				900	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				901
				902	<li><tt>ReplaceInstWithInst</tt>
				903
				904	<p>This function replaces a particular instruction with another
				905	instruction. The following example illustrates the replacement of one
				906	<tt>AllocaInst</tt> with another.</p>
				907
				908	<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]	909	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	910
				911	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				912
				913	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				914	<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
				915	doxygen documentation for the <a href="/doxygen/classValue.html">Value Class</a>
				916	and <a href="/doxygen/classUser.html">User Class</a>, respectively, for more
				917	information.</p>
				918
				919	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				920	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				921	ReplaceInstWithValue, ReplaceInstWithInst -->
				922
				923	</div>
				924
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	925	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	926	<div class="doc_section">
				927	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				928	</div>
				929	<!-- *********************************************************************** -->
				930
				931	<div class="doc_text">
				932
				933	<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]	934	being inspected or transformed. The core LLVM classes are defined in
				935	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	936	the <tt>lib/VMCore</tt> directory.</p>
				937
				938	</div>
				939
				940	<!-- ======================================================================= -->
				941	<div class="doc_subsection">
				942	<a name="Value">The <tt>Value</tt> class</a>
				943	</div>
				944
				945	<div>
				946
				947	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				948	<br>
				949	doxygen info: <a href="/doxygen/classValue.html">Value Class</a></p>
				950
				951	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				952	base. It represents a typed value that may be used (among other things) as an
				953	operand to an instruction. There are many different types of <tt>Value</tt>s,
				954	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				955	href="#Argument"><tt>Argument</tt></a>s. Even <a
				956	href="#Instruction"><tt>Instruction</tt></a>s and <a
				957	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				958
				959	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				960	for a program. For example, an incoming argument to a function (represented
				961	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				962	every instruction in the function that references the argument. To keep track
				963	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				964	href="#User"><tt>User</tt></a>s that is using it (the <a
				965	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				966	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				967	def-use information in the program, and is accessible through the <tt>use_</tt>*
				968	methods, shown below.</p>
				969
				970	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				971	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				972	method. In addition, all LLVM values can be named. The "name" of the
				973	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				974
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	975	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	976
				977	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				978	that the name of any value may be missing (an empty string), so names should
				979	<b>ONLY</b> be used for debugging (making the source code easier to read,
				980	debugging printouts), they should not be used to keep track of values or map
				981	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				982	<tt>Value</tt> itself instead.</p>
				983
				984	<p>One important aspect of LLVM is that there is no distinction between an SSA
				985	variable and the operation that produces it. Because of this, any reference to
				986	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]	987	argument, for example) is represented as a direct pointer to the instance of
				988	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	989	represents this value. Although this may take some getting used to, it
				990	simplifies the representation and makes it easier to manipulate.</p>
				991
				992	</div>
				993
				994	<!-- _______________________________________________________________________ -->
				995	<div class="doc_subsubsection">
				996	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				997	</div>
				998
				999	<div class="doc_text">
				1000
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1001	<ul>
				1002	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1003	use-list<br>
				1004	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1005	the use-list<br>
				1006	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1007	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1008	<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]	1009	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1010	the use-list.<br>
				1011	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1012	use-list.<br>
				1013	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1014	element in the list.
				1015	<p> These methods are the interface to access the def-use
				1016	information in LLVM. As with all other iterators in LLVM, the naming
				1017	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]	1018	</li>
				1019	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1020	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1021	</li>
				1022	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1023	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1024	<tt>void setName(const std::string &Name)</tt>
				1025	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1026	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1027	</li>
				1028	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1029
				1030	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1031	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1032	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1033	produces a constant value (for example through constant folding), you can
				1034	replace all uses of the instruction with the constant like this:</p>
				1035
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1036	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1037	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1038
				1039	</div>
				1040
				1041	<!-- ======================================================================= -->
				1042	<div class="doc_subsection">
				1043	<a name="User">The <tt>User</tt> class</a>
				1044	</div>
				1045
				1046	<div class="doc_text">
				1047
				1048	<p>
				1049	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1050	doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1051	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1052
				1053	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1054	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1055	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1056	referring to. The <tt>User</tt> class itself is a subclass of
				1057	<tt>Value</tt>.</p>
				1058
				1059	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1060	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1061	Single Assignment (SSA) form, there can only be one definition referred to,
				1062	allowing this direct connection. This connection provides the use-def
				1063	information in LLVM.</p>
				1064
				1065	</div>
				1066
				1067	<!-- _______________________________________________________________________ -->
				1068	<div class="doc_subsubsection">
				1069	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1070	</div>
				1071
				1072	<div class="doc_text">
				1073
				1074	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1075	an index access interface and through an iterator based interface.</p>
				1076
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1077	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1078	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1079	<tt>unsigned getNumOperands()</tt>
				1080	<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]	1081	convenient form for direct access.</p></li>
				1082
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1083	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1084	list<br>
				1085	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1086	Get an iterator to the start of the operand list.<br>
				1087	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1088	operand list.
				1089	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1090	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1091	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1092
				1093	</div>
				1094
				1095	<!-- ======================================================================= -->
				1096	<div class="doc_subsection">
				1097	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1098	</div>
				1099
				1100	<div class="doc_text">
				1101
				1102	<p><tt>#include "</tt><tt><a
				1103	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
				1104	doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
				1105	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1106	href="#Value"><tt>Value</tt></a></p>
				1107
				1108	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1109	instructions. It provides only a few methods, but is a very commonly used
				1110	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1111	opcode (instruction type) and the parent <a
				1112	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1113	into. To represent a specific type of instruction, one of many subclasses of
				1114	<tt>Instruction</tt> are used.</p>
				1115
				1116	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1117	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1118	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1119	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1120	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1121	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1122	file contains some meta-data about the various different types of instructions
				1123	in LLVM. It describes the enum values that are used as opcodes (for example
				1124	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1125	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1126	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1127	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1128	this file confuses doxygen, so these enum values don't show up correctly in the
				1129	<a href="/doxygen/classInstruction.html">doxygen output</a>.</p>
				1130
				1131	</div>
				1132
				1133	<!-- _______________________________________________________________________ -->
				1134	<div class="doc_subsubsection">
				1135	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1136	class</a>
				1137	</div>
				1138
				1139	<div class="doc_text">
				1140
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1141	<ul>
				1142	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1143	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1144	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1145	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1146	<p>Returns true if the instruction writes to memory, i.e. it is a
				1147	<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]	1148	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1149	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1150	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1151	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1152	in all ways to the original except that the instruction has no parent
				1153	(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]	1154	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1155	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1156
				1157	</div>
				1158
				1159	<!-- ======================================================================= -->
				1160	<div class="doc_subsection">
				1161	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1162	</div>
				1163
				1164	<div class="doc_text">
				1165
				1166	<p><tt>#include "<a href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1167	doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1168	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1169
				1170	<p>This class represents a single entry multiple exit section of the code,
				1171	commonly known as a basic block by the compiler community. The
				1172	<tt>BasicBlock</tt> class maintains a list of <a
				1173	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1174	Matching the language definition, the last element of this list of instructions
				1175	is always a terminator instruction (a subclass of the <a
				1176	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1177
				1178	<p>In addition to tracking the list of instructions that make up the block, the
				1179	<tt>BasicBlock</tt> class also keeps track of the <a
				1180	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1181
				1182	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1183	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1184	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1185	<tt>label</tt>.</p>
				1186
				1187	</div>
				1188
				1189	<!-- _______________________________________________________________________ -->
				1190	<div class="doc_subsubsection">
				1191	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1192	class</a>
				1193	</div>
				1194
				1195	<div class="doc_text">
				1196
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1197	<ul>
				1198	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
				1199	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1200	<p>The <tt>BasicBlock</tt> constructor is used to create new basic
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1201	blocks for insertion into a function. The constructor optionally takes
				1202	a name for the new block, and a <a href="#Function"><tt>Function</tt></a>
				1203	to insert it into. If the <tt>Parent</tt> parameter is specified, the
				1204	new <tt>BasicBlock</tt> is automatically inserted at the end of the
				1205	specified <a href="#Function"><tt>Function</tt></a>, if not specified,
				1206	the BasicBlock must be manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1207	</li>
				1208	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list
				1209	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1210	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1211	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,<tt>size()</tt>,<tt>empty()</tt>,<tt>rbegin()</tt>,<tt>rend()
				1212	- </tt>STL style functions for accessing the instruction list.
				1213	<p> These methods and typedefs are forwarding functions that have
				1214	the same semantics as the standard library methods of the same names.
				1215	These methods expose the underlying instruction list of a basic block in
				1216	a way that is easy to manipulate. To get the full complement of
				1217	container operations (including operations to update the list), you must
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1218	use the <tt>getInstList()</tt> method.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1219	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1220	<p> This method is used to get access to the underlying container
				1221	that actually holds the Instructions. This method must be used when
				1222	there isn't a forwarding function in the <tt>BasicBlock</tt> class for
				1223	the operation that you would like to perform. Because there are no
				1224	forwarding functions for "updating" operations, you need to use this if
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1225	you want to update the contents of a <tt>BasicBlock</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1226	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1227	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1228	the block is embedded into, or a null pointer if it is homeless.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1229	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1230	<p> Returns a pointer to the terminator instruction that appears at
				1231	the end of the <tt>BasicBlock</tt>. If there is no terminator
				1232	instruction, or if the last instruction in the block is not a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1233	terminator, then a null pointer is returned.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1234	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1235
				1236	</div>
				1237
				1238	<!-- ======================================================================= -->
				1239	<div class="doc_subsection">
				1240	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1241	</div>
				1242
				1243	<div class="doc_text">
				1244
				1245	<p><tt>#include "<a
				1246	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
				1247	doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
				1248	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1249	href="#Value"><tt>Value</tt></a></p>
				1250
				1251	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1252	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1253	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1254	Because they are visible at global scope, they are also subject to linking with
				1255	other globals defined in different translation units. To control the linking
				1256	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1257	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
				1258	defined by the <tt>LinkageTypes</tt> enumerator.</p>
				1259
				1260	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1261	<tt>static</tt> in C), it is not visible to code outside the current translation
				1262	unit, and does not participate in linking. If it has external linkage, it is
				1263	visible to external code, and does participate in linking. In addition to
				1264	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1265	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1266
				1267	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1268	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1269	global is always a pointer to its contents. It is important to remember this
				1270	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1271	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1272	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1273	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1274	the address of the first element of this array and the value of the
				1275	<tt>GlobalVariable</tt> are the same, they have different types. The
				1276	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1277	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1278	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1279	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1280	Language Reference Manual</a>.</p>
				1281
				1282	</div>
				1283
				1284	<!-- _______________________________________________________________________ -->
				1285	<div class="doc_subsubsection">
				1286	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1287	class</a>
				1288	</div>
				1289
				1290	<div class="doc_text">
				1291
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1292	<ul>
				1293	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1294	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1295	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1296	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1297	<p> </p>
				1298	</li>
				1299	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1300	<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]	1301	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1302	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1303
				1304	</div>
				1305
				1306	<!-- ======================================================================= -->
				1307	<div class="doc_subsection">
				1308	<a name="Function">The <tt>Function</tt> class</a>
				1309	</div>
				1310
				1311	<div class="doc_text">
				1312
				1313	<p><tt>#include "<a
				1314	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
				1315	info: <a href="/doxygen/classFunction.html">Function Class</a><br> Superclasses:
				1316	<a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1317	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1318
				1319	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1320	actually one of the more complex classes in the LLVM heirarchy because it must
				1321	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1322	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1323	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1324	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1325
				1326	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1327	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1328	ordering of the blocks in the function, which indicate how the code will be
				1329	layed out by the backend. Additionally, the first <a
				1330	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1331	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1332	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1333	nodes from a single <tt>Function</tt>. If the <a
				1334	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1335	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1336	function hasn't been linked in yet.</p>
				1337
				1338	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1339	<tt>Function</tt> class also keeps track of the list of formal <a
				1340	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1341	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1342	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1343	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1344
				1345	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1346	LLVM feature that is only used when you have to look up a value by name. Aside
				1347	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1348	internally to make sure that there are not conflicts between the names of <a
				1349	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1350	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1351	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1352
				1353	</div>
				1354
				1355	<!-- _______________________________________________________________________ -->
				1356	<div class="doc_subsubsection">
				1357	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1358	class</a>
				1359	</div>
				1360
				1361	<div class="doc_text">
				1362
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1363	<ul>
				1364	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1365	Ty, bool isInternal, const std::string &N = "", Module Parent = 0)</tt>
				1366
				1367	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1368	the the program. The constructor must specify the type of the function to
				1369	create and whether or not it should start out with internal or external
				1370	linkage. The <a href="#FunctionType"><tt>FunctionType</tt></a> argument
				1371	specifies the formal arguments and return value for the function. The same
				1372	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1373	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1374	in which the function is defined. If this argument is provided, the function
				1375	will automatically be inserted into that module's list of
				1376	functions.</p></li>
				1377
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1378	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1379
				1380	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1381	function is "external", it does not have a body, and thus must be resolved
				1382	by linking with a function defined in a different translation unit.</p></li>
				1383
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1384	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1385	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1386
				1387	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1388	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1389
				1390	<p>These are forwarding methods that make it easy to access the contents of
				1391	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1392	list.</p></li>
				1393
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1394	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1395
				1396	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1397	is necessary to use when you need to update the list or perform a complex
				1398	action that doesn't have a forwarding method.</p></li>
				1399
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1400	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1401	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1402	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1403
				1404	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1405	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1406
				1407	<p>These are forwarding methods that make it easy to access the contents of
				1408	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1409	list.</p></li>
				1410
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1411	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1412
				1413	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1414	necessary to use when you need to update the list or perform a complex
				1415	action that doesn't have a forwarding method.</p></li>
				1416
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1417	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1418
				1419	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1420	function. Because the entry block for the function is always the first
				1421	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1422
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1423	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1424	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1425
				1426	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1427	<tt>Function</tt> and returns the return type of the function, or the <a
				1428	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1429	function.</p></li>
				1430
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1431	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1432
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1433	<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]	1434	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1435	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1436
				1437	</div>
				1438
				1439	<!-- ======================================================================= -->
				1440	<div class="doc_subsection">
				1441	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1442	</div>
				1443
				1444	<div class="doc_text">
				1445
				1446	<p><tt>#include "<a
				1447	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1448	<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1449	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1450	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1451	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1452
				1453	<p>Global variables are represented with the (suprise suprise)
				1454	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1455	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1456	always referenced by their address (global values must live in memory, so their
				1457	"name" refers to their address). See <a
				1458	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1459	may have an initial value (which must be a <a
				1460	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1461	may be marked as "constant" themselves (indicating that their contents never
				1462	change at runtime).</p>
				1463
				1464	</div>
				1465
				1466	<!-- _______________________________________________________________________ -->
				1467	<div class="doc_subsubsection">
				1468	<a name="m_GlobalVariable">Important Public Members of the
				1469	<tt>GlobalVariable</tt> class</a>
				1470	</div>
				1471
				1472	<div class="doc_text">
				1473
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1474	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1475	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1476	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1477	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1478
				1479	<p>Create a new global variable of the specified type. If
				1480	<tt>isConstant</tt> is true then the global variable will be marked as
				1481	unchanging for the program. The Linkage parameter specifies the type of
				1482	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1483	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1484	the resultant global variable will have internal linkage. AppendingLinkage
				1485	concatenates together all instances (in different translation units) of the
				1486	variable into a single variable but is only applicable to arrays.  See
				1487	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1488	further details on linkage types. Optionally an initializer, a name, and the
				1489	module to put the variable into may be specified for the global variable as
				1490	well.</p></li>
				1491
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1492	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1493
				1494	<p>Returns true if this is a global variable that is known not to
				1495	be modified at runtime.</p></li>
				1496
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1497	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1498
				1499	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1500
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1501	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1502
				1503	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1504	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1505	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1506
				1507	</div>
				1508
				1509	<!-- ======================================================================= -->
				1510	<div class="doc_subsection">
				1511	<a name="Module">The <tt>Module</tt> class</a>
				1512	</div>
				1513
				1514	<div class="doc_text">
				1515
				1516	<p><tt>#include "<a
				1517	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
				1518	<a href="/doxygen/classModule.html">Module Class</a></p>
				1519
				1520	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1521	programs. An LLVM module is effectively either a translation unit of the
				1522	original program or a combination of several translation units merged by the
				1523	linker. The <tt>Module</tt> class keeps track of a list of <a
				1524	href="#Function"><tt>Function</tt></a>s, a list of <a
				1525	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1526	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1527	helpful member functions that try to make common operations easy.</p>
				1528
				1529	</div>
				1530
				1531	<!-- _______________________________________________________________________ -->
				1532	<div class="doc_subsubsection">
				1533	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1534	</div>
				1535
				1536	<div class="doc_text">
				1537
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1538	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1539	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1540	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1541
				1542	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1543	provide a name for it (probably based on the name of the translation unit).</p>
				1544
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1545	<ul>
				1546	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1547	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1548
				1549	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1550	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1551
				1552	<p>These are forwarding methods that make it easy to access the contents of
				1553	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1554	list.</p></li>
				1555
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1556	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1557
				1558	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1559	necessary to use when you need to update the list or perform a complex
				1560	action that doesn't have a forwarding method.</p>
				1561
				1562	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1563	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1564
				1565	<hr>
				1566
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1567	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1568	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1569
				1570	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1571
				1572	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1573	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1574
				1575	<p> These are forwarding methods that make it easy to access the contents of
				1576	a <tt>Module</tt> object's <a
				1577	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1578
				1579	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1580
				1581	<p>Returns the list of <a
				1582	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1583	use when you need to update the list or perform a complex action that
				1584	doesn't have a forwarding method.</p>
				1585
				1586	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1587	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1588
				1589	<hr>
				1590
				1591	<ul>
				1592	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1593
				1594	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1595	for this <tt>Module</tt>.</p>
				1596
				1597	<p><!-- Convenience methods --></p></li>
				1598	</ul>
				1599
				1600	<hr>
				1601
				1602	<ul>
				1603	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1604	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1605
				1606	<p>Look up the specified function in the <tt>Module</tt> <a
				1607	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1608	<tt>null</tt>.</p></li>
				1609
				1610	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1611	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1612
				1613	<p>Look up the specified function in the <tt>Module</tt> <a
				1614	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1615	external declaration for the function and return it.</p></li>
				1616
				1617	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1618
				1619	<p>If there is at least one entry in the <a
				1620	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1621	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1622	string.</p></li>
				1623
				1624	<li><tt>bool addTypeName(const std::string &Name, const <a
				1625	href="#Type">Type</a> *Ty)</tt>
				1626
				1627	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1628	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1629	name, true is returned and the <a
				1630	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1631	</ul>
				1632
				1633	</div>
				1634
				1635	<!-- ======================================================================= -->
				1636	<div class="doc_subsection">
				1637	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1638	</div>
				1639
				1640	<div class="doc_text">
				1641
				1642	<p>Constant represents a base class for different types of constants. It
				1643	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1644	ConstantArray etc for representing the various types of Constants.</p>
				1645
				1646	</div>
				1647
				1648	<!-- _______________________________________________________________________ -->
				1649	<div class="doc_subsubsection">
				1650	<a name="m_Value">Important Public Methods</a>
				1651	</div>
				1652
				1653	<div class="doc_text">
				1654
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1655	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1656	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a
				1657	ConstantExpr
				1658	<hr> Important Subclasses of Constant
				1659	<p> </p>
				1660	<ul>
				1661	<li>ConstantSInt : This subclass of Constant represents a signed
				1662	integer constant.
				1663	<ul>
				1664	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1665	this constant. </li>
				1666	</ul>
				1667	</li>
				1668	<li>ConstantUInt : This class represents an unsigned integer.
				1669	<ul>
				1670	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value
				1671	of this constant. </li>
				1672	</ul>
				1673	</li>
				1674	<li>ConstantFP : This class represents a floating point constant.
				1675	<ul>
				1676	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1677	this constant. </li>
				1678	</ul>
				1679	</li>
				1680	<li>ConstantBool : This represents a boolean constant.
				1681	<ul>
				1682	<li><tt>bool getValue() const</tt>: Returns the underlying value of
				1683	this constant. </li>
				1684	</ul>
				1685	</li>
				1686	<li>ConstantArray : This represents a constant array.
				1687	<ul>
				1688	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1689	Returns a Vecotr of component constants that makeup this array. </li>
				1690	</ul>
				1691	</li>
				1692	<li>ConstantStruct : This represents a constant struct.
				1693	<ul>
				1694	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1695	Returns a Vecotr of component constants that makeup this array. </li>
				1696	</ul>
				1697	</li>
				1698	<li>ConstantPointerRef : This represents a constant pointer value
				1699	that is initialized to point to a global value, which lies at a
				1700	constant fixed address.
				1701	<ul>
				1702	<li><tt>GlobalValue *getValue()</tt>: Returns the global
				1703	value to which this pointer is pointing to. </li>
				1704	</ul>
				1705	</li>
				1706	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1707	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1708	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1709
				1710	</div>
				1711
				1712	<!-- ======================================================================= -->
				1713	<div class="doc_subsection">
				1714	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1715	</div>
				1716
				1717	<div class="doc_text">
				1718
				1719	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1720	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1721	types are instances of subclasses of type like FunctionType, ArrayType
				1722	etc. DerivedType is the interface for all such dervied types including
				1723	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1724	be recursive (StructType). There exists exactly one instance of any type
				1725	structure at a time. This allows using pointer equality of Type *s for comparing
				1726	types.</p>
				1727
				1728	</div>
				1729
				1730	<!-- _______________________________________________________________________ -->
				1731	<div class="doc_subsubsection">
				1732	<a name="m_Value">Important Public Methods</a>
				1733	</div>
				1734
				1735	<div class="doc_text">
				1736
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1737	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1738
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1739	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1740	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1741	not true for Float and Double. </li>
				1742
				1743	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1744	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1745	return false as they do with isSigned. This returns true for UByteTy,
				1746	UShortTy, UIntTy, and ULongTy. </li>
				1747
				1748	<li><tt>bool isInteger() const</tt>: Equilivent to isSigned() \|\| isUnsigned(),
				1749	but with only a single virtual function invocation.</li>
				1750
				1751	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1752	type, which is either Bool type or one of the Integer types.</li>
				1753
				1754	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1755	floating point types.</li>
				1756
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1757	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1758	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]	1759	example, uint to int or one pointer type to another.</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1760
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1761	<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1762	<p>Derived Types</p>
				1763
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1764	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1765	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1766	<ul>
				1767	<li><tt>const Type * getElementType() const</tt>: Returns the type of
				1768	each of the elements in the sequential type. </li>
				1769	</ul>
				1770	</li>
				1771	<li>ArrayType : This is a subclass of SequentialType and defines
				1772	interface for array types.
				1773	<ul>
				1774	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1775	elements in the array. </li>
				1776	</ul>
				1777	</li>
				1778	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1779	<li>StructType : subclass of DerivedTypes for struct types </li>
				1780	<li>FunctionType : subclass of DerivedTypes for function types.
				1781	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1782	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1783	function</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1784	<li><tt> const Type * getReturnType() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1785	return type of the function.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1786	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1787	the type of the ith parameter.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1788	<li><tt> const unsigned getNumParams() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1789	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1790	</ul>
				1791	</li>
				1792	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1793	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1794	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1795
				1796	</div>
				1797
				1798	<!-- ======================================================================= -->
				1799	<div class="doc_subsection">
				1800	<a name="Argument">The <tt>Argument</tt> class</a>
				1801	</div>
				1802
				1803	<div class="doc_text">
				1804
				1805	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1806	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1807	arguments. An argument has a pointer to the parent Function.</p>
				1808
				1809	</div>
				1810
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1811	<!-- ======================================================================= -->
				1812	<div class="doc_subsection">
				1813	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1814	</div>
				1815	<div class="doc_text">
				1816	<p>This class provides a symbol table that the
				1817	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1818	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1819	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1820	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1821	type. It hides the data it contains and provides access to it through a
				1822	controlled interface.</p>
				1823
				1824	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1825	structure of the information it holds. The class contains two
				1826	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1827	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1828	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1829	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1830	however, are stored in a single dimension and accessed only by name.</p>
				1831
				1832	<p>The interface of this class provides three basic types of operations:
				1833	<ol>
				1834	<li><em>Accessors</em>. Accessors provide read-only access to information
				1835	such as finding a value for a name with the
				1836	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1837	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1838	<tt>SymbolTable</tt> with methods like
				1839	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1840	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1841	of the symbol table in well defined ways, such as the method
				1842	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1843	</ol>
				1844
				1845	<h3>Accessors</h3>
				1846	<dl>
				1847	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1848	</dt>
				1849	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1850	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1851	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1852
				1853	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1854	<dd>The <tt>lookupType</tt> method searches through the types for a
				1855	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1856	is not found, null is returned.</dd>
				1857
				1858	<dt><tt>bool hasTypes() const</tt>:</dt>
				1859	<dd>This function returns true if an entry has been made into the type
				1860	map.</dd>
				1861
				1862	<dt><tt>bool isEmpty() const</tt>:</dt>
				1863	<dd>This function returns true if both the value and types maps are
				1864	empty</dd>
				1865
				1866	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1867	<dd>This function returns the name of the Value provided or the empty
				1868	string if the Value is not in the symbol table.</dd>
				1869
				1870	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1871	<dd>This function returns the name of the Type provided or the empty
				1872	string if the Type is not in the symbol table.</dd>
				1873	</dl>
				1874
				1875	<h3>Mutators</h3>
				1876	<dl>
				1877	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1878	<dd>This method adds the provided value to the symbol table. The Value must
				1879	have both a name and a type which are extracted and used to place the value
				1880	in the correct type plane under the value's name.</dd>
				1881
				1882	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1883	<dd> Inserts a constant or type into the symbol table with the specified
				1884	name. There can be a many to one mapping between names and constants
				1885	or types.</dd>
				1886
				1887	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1888	<dd> Inserts a type into the symbol table with the specified name. There
				1889	can be a many-to-one mapping between names and types. This method
				1890	allows a type with an existing entry in the symbol table to get
				1891	a new name.</dd>
				1892
				1893	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1894	<dd> This method removes a named value from the symbol table. The
				1895	type and name of the Value are extracted from \p N and used to
				1896	lookup the Value in the correct type plane. If the Value is
				1897	not in the symbol table, this method silently ignores the
				1898	request.</dd>
				1899
				1900	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1901	<dd> This method removes a named type from the symbol table. The
				1902	name of the type is extracted from \P T and used to look up
				1903	the Type in the type map. If the Type is not in the symbol
				1904	table, this method silently ignores the request.</dd>
				1905
				1906	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1907	<dd> Remove a constant or type with the specified name from the
				1908	symbol table.</dd>
				1909
				1910	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1911	<dd> Remove a type with the specified name from the symbol table.
				1912	Returns the removed Type.</dd>
				1913
				1914	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1915	<dd> Removes a specific value from the symbol table.
				1916	Returns the removed value.</dd>
				1917
				1918	<dt><tt>bool strip()</tt>:</dt>
				1919	<dd> This method will strip the symbol table of its names leaving
				1920	the type and values. </dd>
				1921
				1922	<dt><tt>void clear()</tt>:</dt>
				1923	<dd>Empty the symbol table completely.</dd>
				1924	</dl>
				1925
				1926	<h3>Iteration</h3>
				1927	<p>The following functions describe three types of iterators you can obtain
				1928	the beginning or end of the sequence for both const and non-const. It is
				1929	important to keep track of the different kinds of iterators. There are
				1930	three idioms worth pointing out:</p>
				1931	<table class="doc_table">
				1932	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1933	<tr>
				1934	<td>Planes Of name/Value maps</td><td>PI</td>
				1935	<td><tt><pre>
				1936	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
				1937	PE = ST.plane_end(); PI != PE; ++PI ) {
				1938	PI->first // This is the Type* of the plane
				1939	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1940	</pre></tt></td>
				1941	</tr>
				1942	<tr>
				1943	<td>All name/Type Pairs</td><td>TI</td>
				1944	<td><tt><pre>
				1945	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1946	TE = ST.type_end(); TI != TE; ++TI )
				1947	TI->first // This is the name of the type
				1948	TI->second // This is the Type* value associated with the name
				1949	</pre></tt></td>
				1950	</tr>
				1951	<tr>
				1952	<td>name/Value pairs in a plane</td><td>VI</td>
				1953	<td><tt><pre>
				1954	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1955	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1956	VI->first // This is the name of the Value
				1957	VI->second // This is the Value* value associated with the name
				1958	</pre></tt></td>
				1959	</tr>
				1960	</table>
				1961	<p>Using the recommended iterator names and idioms will help you avoid
				1962	making mistakes. Of particular note, make sure that whenever you use
				1963	value_begin(SomeType) that you always compare the resulting iterator
				1964	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1965	will loop infinitely.</p>
				1966
				1967	<dl>
				1968
				1969	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1970	<dd>Get an iterator that starts at the beginning of the type planes.
				1971	The iterator will iterate over the Type/ValueMap pairs in the
				1972	type planes. </dd>
				1973
				1974	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1975	<dd>Get a const_iterator that starts at the beginning of the type
				1976	planes. The iterator will iterate over the Type/ValueMap pairs
				1977	in the type planes. </dd>
				1978
				1979	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1980	<dd>Get an iterator at the end of the type planes. This serves as
				1981	the marker for end of iteration over the type planes.</dd>
				1982
				1983	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				1984	<dd>Get a const_iterator at the end of the type planes. This serves as
				1985	the marker for end of iteration over the type planes.</dd>
				1986
				1987	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1988	<dd>Get an iterator that starts at the beginning of a type plane.
				1989	The iterator will iterate over the name/value pairs in the type plane.
				1990	Note: The type plane must already exist before using this.</dd>
				1991
				1992	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				1993	<dd>Get a const_iterator that starts at the beginning of a type plane.
				1994	The iterator will iterate over the name/value pairs in the type plane.
				1995	Note: The type plane must already exist before using this.</dd>
				1996
				1997	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				1998	<dd>Get an iterator to the end of a type plane. This serves as the marker
				1999	for end of iteration of the type plane.
				2000	Note: The type plane must already exist before using this.</dd>
				2001
				2002	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				2003	<dd>Get a const_iterator to the end of a type plane. This serves as the
				2004	marker for end of iteration of the type plane.
				2005	Note: the type plane must already exist before using this.</dd>
				2006
				2007	<dt><tt>type_iterator type_begin()</tt>:</dt>
				2008	<dd>Get an iterator to the start of the name/Type map.</dd>
				2009
				2010	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				2011	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				2012
				2013	<dt><tt>type_iterator type_end()</tt>:</dt>
				2014	<dd>Get an iterator to the end of the name/Type map. This serves as the
				2015	marker for end of iteration of the types.</dd>
				2016
				2017	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2018	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2019	as the marker for end of iteration of the types.</dd>
				2020
				2021	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2022	<dd>This method returns a plane_const_iterator for iteration over
				2023	the type planes starting at a specific plane, given by \p Ty.</dd>
				2024
				2025	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2026	<dd>This method returns a plane_iterator for iteration over the
				2027	type planes starting at a specific plane, given by \p Ty.</dd>
				2028
				2029	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2030	<dd>This method returns a ValueMap* for a specific type plane. This
				2031	interface is deprecated and may go away in the future.</dd>
				2032	</dl>
				2033	</div>
				2034
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2035	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2036	<hr>
				2037	<address>
				2038	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2039	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2040	<a href="http://validator.w3.org/check/referer"><img
				2041	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2042
				2043	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2044	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2045	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2046	Last modified: $Date$
				2047	</address>
				2048
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2049	</body>
				2050	</html>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	2051	<!-- vim: sw=2 noai
				2052	-->