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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
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				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
				18	<li><a href="#stl">The C++ Standard Template Library</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	19	<li>The <tt>-time-passes</tt> option
				20	<li>How to use the LLVM Makefile system
				21	<li>How to write a regression test
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	22	--> </li>
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	23	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	24	</li>
				25	<li><a href="#apis">Important and useful LLVM APIs</a>
				26	<ul>
				27	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				28	and <tt>dyn_cast<></tt> templates</a> </li>
				29	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				30	option</a>
				31	<ul>
				32	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				33	and the <tt>-debug-only</tt> option</a> </li>
				34	</ul>
				35	</li>
				36	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				37	option</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	38	<li>The <tt>InstVisitor</tt> template
				39	<li>The general graph API
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	40	--> </li>
				41	</ul>
				42	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	43	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	44	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	45	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				46	<ul>
				47	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				48	in a <tt>Function</tt></a> </li>
				49	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				50	in a <tt>BasicBlock</tt></a> </li>
				51	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				52	in a <tt>Function</tt></a> </li>
				53	<li><a href="#iterate_convert">Turning an iterator into a
				54	class pointer</a> </li>
				55	<li><a href="#iterate_complex">Finding call sites: a more
				56	complex example</a> </li>
				57	<li><a href="#calls_and_invokes">Treating calls and invokes
				58	the same way</a> </li>
				59	<li><a href="#iterate_chains">Iterating over def-use &
				60	use-def chains</a> </li>
				61	</ul>
				62	</li>
				63	<li><a href="#simplechanges">Making simple changes</a>
				64	<ul>
				65	<li><a href="#schanges_creating">Creating and inserting new
				66	<tt>Instruction</tt>s</a> </li>
				67	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				68	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				69	with another <tt>Value</tt></a> </li>
				70	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	71	<!--
				72	<li>Working with the Control Flow Graph
				73	<ul>
				74	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				75	<li>
				76	<li>
				77	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	78	--> </li>
				79	</ul>
				80	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	81	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	82	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	83	<li><a href="#Value">The <tt>Value</tt> class</a>
				84	<ul>
				85	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	86	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	87	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	88	<ul>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	89	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt>
				90	class</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	91	</ul></li>
				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
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	693	href="http://llvm.cs.uiuc.edu/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	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
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	714	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				715	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				716	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				717	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				718	particular function <tt>foo</tt>. Finding all of the instructions that
				719	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				720	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	721
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	722	<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]	723
				724	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	725	href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	726	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				727	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				728	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				729	all of the values that a particular instruction uses (that is, the operands of
				730	the particular <tt>Instruction</tt>):</p>
				731
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	732	<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]	733
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	734	<!--
				735	def-use chains ("finding all users of"): Value::use_begin/use_end
				736	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]	737	-->
				738
				739	</div>
				740
				741	<!-- ======================================================================= -->
				742	<div class="doc_subsection">
				743	<a name="simplechanges">Making simple changes</a>
				744	</div>
				745
				746	<div class="doc_text">
				747
				748	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	749	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	750	transformations, it's fairly common to manipulate the contents of basic
				751	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	752	and gives example code.</p>
				753
				754	</div>
				755
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	756	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	757	<div class="doc_subsubsection">
				758	<a name="schanges_creating">Creating and inserting new
				759	<tt>Instruction</tt>s</a>
				760	</div>
				761
				762	<div class="doc_text">
				763
				764	<p><i>Instantiating Instructions</i></p>
				765
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	766	<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]	767	constructor for the kind of instruction to instantiate and provide the necessary
				768	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				769	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				770
				771	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				772
				773	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				774	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				775	subclass is likely to have varying default parameters which change the semantics
				776	of the instruction, so refer to the <a
				777	href="/doxygen/classInstruction.html">doxygen documentation for the subclass of
				778	Instruction</a> that you're interested in instantiating.</p>
				779
				780	<p><i>Naming values</i></p>
				781
				782	<p>It is very useful to name the values of instructions when you're able to, as
				783	this facilitates the debugging of your transformations. If you end up looking
				784	at generated LLVM machine code, you definitely want to have logical names
				785	associated with the results of instructions! By supplying a value for the
				786	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				787	associate a logical name with the result of the instruction's execution at
				788	runtime. For example, say that I'm writing a transformation that dynamically
				789	allocates space for an integer on the stack, and that integer is going to be
				790	used as some kind of index by some other code. To accomplish this, I place an
				791	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				792	<tt>Function</tt>, and I'm intending to use it within the same
				793	<tt>Function</tt>. I might do:</p>
				794
				795	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				796
				797	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				798	execution value, which is a pointer to an integer on the runtime stack.</p>
				799
				800	<p><i>Inserting instructions</i></p>
				801
				802	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				803	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				804
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	805	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	806	<li>Insertion into an explicit instruction list
				807
				808	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				809	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				810	before <tt>*pi</tt>, we do the following: </p>
				811
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	812	<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>
				813
				814	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				815	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				816	classes provide constructors which take a pointer to a
				817	<tt>BasicBlock</tt> to be appended to. For example code that
				818	looked like: </p>
				819
				820	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				821
				822	<p>becomes: </p>
				823
				824	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				825
				826	<p>which is much cleaner, especially if you are creating
				827	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	828
				829	<li>Insertion into an implicit instruction list
				830
				831	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				832	are implicitly associated with an existing instruction list: the instruction
				833	list of the enclosing basic block. Thus, we could have accomplished the same
				834	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				835	</p>
				836
				837	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				838
				839	<p>In fact, this sequence of steps occurs so frequently that the
				840	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				841	constructors which take (as a default parameter) a pointer to an
				842	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				843	precede. That is, <tt>Instruction</tt> constructors are capable of
				844	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				845	provided instruction, immediately before that instruction. Using an
				846	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				847	parameter, the above code becomes:</p>
				848
				849	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				850
				851	<p>which is much cleaner, especially if you're creating a lot of
				852	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				853	</ul>
				854
				855	</div>
				856
				857	<!--_______________________________________________________________________-->
				858	<div class="doc_subsubsection">
				859	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				860	</div>
				861
				862	<div class="doc_text">
				863
				864	<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]	865	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	866	you must have a pointer to the instruction that you wish to delete. Second, you
				867	need to obtain the pointer to that instruction's basic block. You use the
				868	pointer to the basic block to get its list of instructions and then use the
				869	erase function to remove your instruction. For example:</p>
				870
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	871	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				872	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]	873
				874	</div>
				875
				876	<!--_______________________________________________________________________-->
				877	<div class="doc_subsubsection">
				878	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				879	<tt>Value</tt></a>
				880	</div>
				881
				882	<div class="doc_text">
				883
				884	<p><i>Replacing individual instructions</i></p>
				885
				886	<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]	887	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	888	and <tt>ReplaceInstWithInst</tt>.</p>
				889
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	890	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	891
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	892	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	893	<li><tt>ReplaceInstWithValue</tt>
				894
				895	<p>This function replaces all uses (within a basic block) of a given
				896	instruction with a value, and then removes the original instruction. The
				897	following example illustrates the replacement of the result of a particular
				898	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				899	pointer to an integer.</p>
				900
				901	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				902
				903	<li><tt>ReplaceInstWithInst</tt>
				904
				905	<p>This function replaces a particular instruction with another
				906	instruction. The following example illustrates the replacement of one
				907	<tt>AllocaInst</tt> with another.</p>
				908
				909	<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]	910	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	911
				912	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				913
				914	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				915	<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	916	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				917	and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	918	information.</p>
				919
				920	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				921	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				922	ReplaceInstWithValue, ReplaceInstWithInst -->
				923
				924	</div>
				925
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	926	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	927	<div class="doc_section">
				928	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				929	</div>
				930	<!-- *********************************************************************** -->
				931
				932	<div class="doc_text">
				933
				934	<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]	935	being inspected or transformed. The core LLVM classes are defined in
				936	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	937	the <tt>lib/VMCore</tt> directory.</p>
				938
				939	</div>
				940
				941	<!-- ======================================================================= -->
				942	<div class="doc_subsection">
				943	<a name="Value">The <tt>Value</tt> class</a>
				944	</div>
				945
				946	<div>
				947
				948	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				949	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	950	doxygen info: <a href="/doxygen/structllvm_1_1Value.html">Value Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	951
				952	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				953	base. It represents a typed value that may be used (among other things) as an
				954	operand to an instruction. There are many different types of <tt>Value</tt>s,
				955	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				956	href="#Argument"><tt>Argument</tt></a>s. Even <a
				957	href="#Instruction"><tt>Instruction</tt></a>s and <a
				958	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				959
				960	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				961	for a program. For example, an incoming argument to a function (represented
				962	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				963	every instruction in the function that references the argument. To keep track
				964	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				965	href="#User"><tt>User</tt></a>s that is using it (the <a
				966	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				967	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				968	def-use information in the program, and is accessible through the <tt>use_</tt>*
				969	methods, shown below.</p>
				970
				971	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				972	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				973	method. In addition, all LLVM values can be named. The "name" of the
				974	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				975
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	976	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	977
				978	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				979	that the name of any value may be missing (an empty string), so names should
				980	<b>ONLY</b> be used for debugging (making the source code easier to read,
				981	debugging printouts), they should not be used to keep track of values or map
				982	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				983	<tt>Value</tt> itself instead.</p>
				984
				985	<p>One important aspect of LLVM is that there is no distinction between an SSA
				986	variable and the operation that produces it. Because of this, any reference to
				987	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]	988	argument, for example) is represented as a direct pointer to the instance of
				989	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	990	represents this value. Although this may take some getting used to, it
				991	simplifies the representation and makes it easier to manipulate.</p>
				992
				993	</div>
				994
				995	<!-- _______________________________________________________________________ -->
				996	<div class="doc_subsubsection">
				997	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				998	</div>
				999
				1000	<div class="doc_text">
				1001
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1002	<ul>
				1003	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1004	use-list<br>
				1005	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1006	the use-list<br>
				1007	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1008	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1009	<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]	1010	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1011	the use-list.<br>
				1012	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1013	use-list.<br>
				1014	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1015	element in the list.
				1016	<p> These methods are the interface to access the def-use
				1017	information in LLVM. As with all other iterators in LLVM, the naming
				1018	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]	1019	</li>
				1020	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1021	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1022	</li>
				1023	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1024	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1025	<tt>void setName(const std::string &Name)</tt>
				1026	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1027	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1028	</li>
				1029	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1030
				1031	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1032	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1033	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1034	produces a constant value (for example through constant folding), you can
				1035	replace all uses of the instruction with the constant like this:</p>
				1036
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1037	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1038	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1039
				1040	</div>
				1041
				1042	<!-- ======================================================================= -->
				1043	<div class="doc_subsection">
				1044	<a name="User">The <tt>User</tt> class</a>
				1045	</div>
				1046
				1047	<div class="doc_text">
				1048
				1049	<p>
				1050	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1051	doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1052	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1053
				1054	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1055	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1056	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1057	referring to. The <tt>User</tt> class itself is a subclass of
				1058	<tt>Value</tt>.</p>
				1059
				1060	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1061	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1062	Single Assignment (SSA) form, there can only be one definition referred to,
				1063	allowing this direct connection. This connection provides the use-def
				1064	information in LLVM.</p>
				1065
				1066	</div>
				1067
				1068	<!-- _______________________________________________________________________ -->
				1069	<div class="doc_subsubsection">
				1070	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1071	</div>
				1072
				1073	<div class="doc_text">
				1074
				1075	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1076	an index access interface and through an iterator based interface.</p>
				1077
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1078	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1079	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1080	<tt>unsigned getNumOperands()</tt>
				1081	<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]	1082	convenient form for direct access.</p></li>
				1083
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1084	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1085	list<br>
				1086	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1087	Get an iterator to the start of the operand list.<br>
				1088	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1089	operand list.
				1090	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1091	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1092	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1093
				1094	</div>
				1095
				1096	<!-- ======================================================================= -->
				1097	<div class="doc_subsection">
				1098	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1099	</div>
				1100
				1101	<div class="doc_text">
				1102
				1103	<p><tt>#include "</tt><tt><a
				1104	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
				1105	doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
				1106	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1107	href="#Value"><tt>Value</tt></a></p>
				1108
				1109	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1110	instructions. It provides only a few methods, but is a very commonly used
				1111	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1112	opcode (instruction type) and the parent <a
				1113	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1114	into. To represent a specific type of instruction, one of many subclasses of
				1115	<tt>Instruction</tt> are used.</p>
				1116
				1117	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1118	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1119	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1120	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1121	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1122	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1123	file contains some meta-data about the various different types of instructions
				1124	in LLVM. It describes the enum values that are used as opcodes (for example
				1125	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1126	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1127	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1128	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1129	this file confuses doxygen, so these enum values don't show up correctly in the
				1130	<a href="/doxygen/classInstruction.html">doxygen output</a>.</p>
				1131
				1132	</div>
				1133
				1134	<!-- _______________________________________________________________________ -->
				1135	<div class="doc_subsubsection">
				1136	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1137	class</a>
				1138	</div>
				1139
				1140	<div class="doc_text">
				1141
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1142	<ul>
				1143	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1144	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1145	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1146	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1147	<p>Returns true if the instruction writes to memory, i.e. it is a
				1148	<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]	1149	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1150	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1151	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1152	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1153	in all ways to the original except that the instruction has no parent
				1154	(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]	1155	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1156	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1157
				1158	</div>
				1159
				1160	<!-- ======================================================================= -->
				1161	<div class="doc_subsection">
				1162	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1163	</div>
				1164
				1165	<div class="doc_text">
				1166
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1167	<p><tt>#include "<a
				1168	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1169	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1170	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1171	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1172
				1173	<p>This class represents a single entry multiple exit section of the code,
				1174	commonly known as a basic block by the compiler community. The
				1175	<tt>BasicBlock</tt> class maintains a list of <a
				1176	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1177	Matching the language definition, the last element of this list of instructions
				1178	is always a terminator instruction (a subclass of the <a
				1179	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1180
				1181	<p>In addition to tracking the list of instructions that make up the block, the
				1182	<tt>BasicBlock</tt> class also keeps track of the <a
				1183	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1184
				1185	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1186	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1187	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1188	<tt>label</tt>.</p>
				1189
				1190	</div>
				1191
				1192	<!-- _______________________________________________________________________ -->
				1193	<div class="doc_subsubsection">
				1194	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1195	class</a>
				1196	</div>
				1197
				1198	<div class="doc_text">
				1199
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1200	<ul>
				1201	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
				1202	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1203	<p>The <tt>BasicBlock</tt> constructor is used to create new basic
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1204	blocks for insertion into a function. The constructor optionally takes
				1205	a name for the new block, and a <a href="#Function"><tt>Function</tt></a>
				1206	to insert it into. If the <tt>Parent</tt> parameter is specified, the
				1207	new <tt>BasicBlock</tt> is automatically inserted at the end of the
				1208	specified <a href="#Function"><tt>Function</tt></a>, if not specified,
				1209	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]	1210	</li>
				1211	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list
				1212	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1213	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1214	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,<tt>size()</tt>,<tt>empty()</tt>,<tt>rbegin()</tt>,<tt>rend()
				1215	- </tt>STL style functions for accessing the instruction list.
				1216	<p> These methods and typedefs are forwarding functions that have
				1217	the same semantics as the standard library methods of the same names.
				1218	These methods expose the underlying instruction list of a basic block in
				1219	a way that is easy to manipulate. To get the full complement of
				1220	container operations (including operations to update the list), you must
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1221	use the <tt>getInstList()</tt> method.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1222	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1223	<p> This method is used to get access to the underlying container
				1224	that actually holds the Instructions. This method must be used when
				1225	there isn't a forwarding function in the <tt>BasicBlock</tt> class for
				1226	the operation that you would like to perform. Because there are no
				1227	forwarding functions for "updating" operations, you need to use this if
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1228	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]	1229	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1230	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1231	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]	1232	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1233	<p> Returns a pointer to the terminator instruction that appears at
				1234	the end of the <tt>BasicBlock</tt>. If there is no terminator
				1235	instruction, or if the last instruction in the block is not a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1236	terminator, then a null pointer is returned.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1237	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1238
				1239	</div>
				1240
				1241	<!-- ======================================================================= -->
				1242	<div class="doc_subsection">
				1243	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1244	</div>
				1245
				1246	<div class="doc_text">
				1247
				1248	<p><tt>#include "<a
				1249	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1250	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1251	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1252	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1253	href="#Value"><tt>Value</tt></a></p>
				1254
				1255	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1256	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1257	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1258	Because they are visible at global scope, they are also subject to linking with
				1259	other globals defined in different translation units. To control the linking
				1260	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1261	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
				1262	defined by the <tt>LinkageTypes</tt> enumerator.</p>
				1263
				1264	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1265	<tt>static</tt> in C), it is not visible to code outside the current translation
				1266	unit, and does not participate in linking. If it has external linkage, it is
				1267	visible to external code, and does participate in linking. In addition to
				1268	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1269	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1270
				1271	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1272	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1273	global is always a pointer to its contents. It is important to remember this
				1274	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1275	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1276	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1277	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1278	the address of the first element of this array and the value of the
				1279	<tt>GlobalVariable</tt> are the same, they have different types. The
				1280	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1281	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1282	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1283	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1284	Language Reference Manual</a>.</p>
				1285
				1286	</div>
				1287
				1288	<!-- _______________________________________________________________________ -->
				1289	<div class="doc_subsubsection">
				1290	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1291	class</a>
				1292	</div>
				1293
				1294	<div class="doc_text">
				1295
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1296	<ul>
				1297	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1298	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1299	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1300	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1301	<p> </p>
				1302	</li>
				1303	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1304	<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]	1305	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1306	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1307
				1308	</div>
				1309
				1310	<!-- ======================================================================= -->
				1311	<div class="doc_subsection">
				1312	<a name="Function">The <tt>Function</tt> class</a>
				1313	</div>
				1314
				1315	<div class="doc_text">
				1316
				1317	<p><tt>#include "<a
				1318	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
				1319	info: <a href="/doxygen/classFunction.html">Function Class</a><br> Superclasses:
				1320	<a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1321	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1322
				1323	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1324	actually one of the more complex classes in the LLVM heirarchy because it must
				1325	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1326	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1327	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1328	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1329
				1330	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1331	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1332	ordering of the blocks in the function, which indicate how the code will be
				1333	layed out by the backend. Additionally, the first <a
				1334	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1335	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1336	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1337	nodes from a single <tt>Function</tt>. If the <a
				1338	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1339	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1340	function hasn't been linked in yet.</p>
				1341
				1342	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1343	<tt>Function</tt> class also keeps track of the list of formal <a
				1344	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1345	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1346	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1347	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1348
				1349	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1350	LLVM feature that is only used when you have to look up a value by name. Aside
				1351	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1352	internally to make sure that there are not conflicts between the names of <a
				1353	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1354	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1355	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1356
				1357	</div>
				1358
				1359	<!-- _______________________________________________________________________ -->
				1360	<div class="doc_subsubsection">
				1361	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1362	class</a>
				1363	</div>
				1364
				1365	<div class="doc_text">
				1366
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1367	<ul>
				1368	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1369	Ty, bool isInternal, const std::string &N = "", Module Parent = 0)</tt>
				1370
				1371	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1372	the the program. The constructor must specify the type of the function to
				1373	create and whether or not it should start out with internal or external
				1374	linkage. The <a href="#FunctionType"><tt>FunctionType</tt></a> argument
				1375	specifies the formal arguments and return value for the function. The same
				1376	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1377	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1378	in which the function is defined. If this argument is provided, the function
				1379	will automatically be inserted into that module's list of
				1380	functions.</p></li>
				1381
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1382	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1383
				1384	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1385	function is "external", it does not have a body, and thus must be resolved
				1386	by linking with a function defined in a different translation unit.</p></li>
				1387
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1388	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1389	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1390
				1391	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1392	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1393
				1394	<p>These are forwarding methods that make it easy to access the contents of
				1395	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1396	list.</p></li>
				1397
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1398	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1399
				1400	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1401	is necessary to use when you need to update the list or perform a complex
				1402	action that doesn't have a forwarding method.</p></li>
				1403
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1404	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1405	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1406	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1407
				1408	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1409	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1410
				1411	<p>These are forwarding methods that make it easy to access the contents of
				1412	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1413	list.</p></li>
				1414
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1415	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1416
				1417	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1418	necessary to use when you need to update the list or perform a complex
				1419	action that doesn't have a forwarding method.</p></li>
				1420
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1421	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1422
				1423	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1424	function. Because the entry block for the function is always the first
				1425	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1426
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1427	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1428	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1429
				1430	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1431	<tt>Function</tt> and returns the return type of the function, or the <a
				1432	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1433	function.</p></li>
				1434
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1435	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1436
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1437	<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]	1438	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1439	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1440
				1441	</div>
				1442
				1443	<!-- ======================================================================= -->
				1444	<div class="doc_subsection">
				1445	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1446	</div>
				1447
				1448	<div class="doc_text">
				1449
				1450	<p><tt>#include "<a
				1451	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1452	<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1453	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1454	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1455	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1456
				1457	<p>Global variables are represented with the (suprise suprise)
				1458	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1459	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1460	always referenced by their address (global values must live in memory, so their
				1461	"name" refers to their address). See <a
				1462	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1463	may have an initial value (which must be a <a
				1464	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1465	may be marked as "constant" themselves (indicating that their contents never
				1466	change at runtime).</p>
				1467
				1468	</div>
				1469
				1470	<!-- _______________________________________________________________________ -->
				1471	<div class="doc_subsubsection">
				1472	<a name="m_GlobalVariable">Important Public Members of the
				1473	<tt>GlobalVariable</tt> class</a>
				1474	</div>
				1475
				1476	<div class="doc_text">
				1477
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1478	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1479	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1480	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1481	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1482
				1483	<p>Create a new global variable of the specified type. If
				1484	<tt>isConstant</tt> is true then the global variable will be marked as
				1485	unchanging for the program. The Linkage parameter specifies the type of
				1486	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1487	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1488	the resultant global variable will have internal linkage. AppendingLinkage
				1489	concatenates together all instances (in different translation units) of the
				1490	variable into a single variable but is only applicable to arrays.  See
				1491	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1492	further details on linkage types. Optionally an initializer, a name, and the
				1493	module to put the variable into may be specified for the global variable as
				1494	well.</p></li>
				1495
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1496	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1497
				1498	<p>Returns true if this is a global variable that is known not to
				1499	be modified at runtime.</p></li>
				1500
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1501	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1502
				1503	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1504
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1505	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1506
				1507	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1508	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1509	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1510
				1511	</div>
				1512
				1513	<!-- ======================================================================= -->
				1514	<div class="doc_subsection">
				1515	<a name="Module">The <tt>Module</tt> class</a>
				1516	</div>
				1517
				1518	<div class="doc_text">
				1519
				1520	<p><tt>#include "<a
				1521	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
				1522	<a href="/doxygen/classModule.html">Module Class</a></p>
				1523
				1524	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1525	programs. An LLVM module is effectively either a translation unit of the
				1526	original program or a combination of several translation units merged by the
				1527	linker. The <tt>Module</tt> class keeps track of a list of <a
				1528	href="#Function"><tt>Function</tt></a>s, a list of <a
				1529	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1530	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1531	helpful member functions that try to make common operations easy.</p>
				1532
				1533	</div>
				1534
				1535	<!-- _______________________________________________________________________ -->
				1536	<div class="doc_subsubsection">
				1537	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1538	</div>
				1539
				1540	<div class="doc_text">
				1541
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1542	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1543	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1544	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1545
				1546	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1547	provide a name for it (probably based on the name of the translation unit).</p>
				1548
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1549	<ul>
				1550	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1551	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1552
				1553	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1554	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1555
				1556	<p>These are forwarding methods that make it easy to access the contents of
				1557	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1558	list.</p></li>
				1559
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1560	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1561
				1562	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1563	necessary to use when you need to update the list or perform a complex
				1564	action that doesn't have a forwarding method.</p>
				1565
				1566	<p><!-- Global Variable --></p></li>
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
				1569	<hr>
				1570
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1571	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1572	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1573
				1574	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1575
				1576	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1577	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1578
				1579	<p> These are forwarding methods that make it easy to access the contents of
				1580	a <tt>Module</tt> object's <a
				1581	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1582
				1583	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1584
				1585	<p>Returns the list of <a
				1586	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1587	use when you need to update the list or perform a complex action that
				1588	doesn't have a forwarding method.</p>
				1589
				1590	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1591	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1592
				1593	<hr>
				1594
				1595	<ul>
				1596	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1597
				1598	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1599	for this <tt>Module</tt>.</p>
				1600
				1601	<p><!-- Convenience methods --></p></li>
				1602	</ul>
				1603
				1604	<hr>
				1605
				1606	<ul>
				1607	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1608	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1609
				1610	<p>Look up the specified function in the <tt>Module</tt> <a
				1611	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1612	<tt>null</tt>.</p></li>
				1613
				1614	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1615	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1616
				1617	<p>Look up the specified function in the <tt>Module</tt> <a
				1618	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1619	external declaration for the function and return it.</p></li>
				1620
				1621	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1622
				1623	<p>If there is at least one entry in the <a
				1624	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1625	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1626	string.</p></li>
				1627
				1628	<li><tt>bool addTypeName(const std::string &Name, const <a
				1629	href="#Type">Type</a> *Ty)</tt>
				1630
				1631	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1632	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1633	name, true is returned and the <a
				1634	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1635	</ul>
				1636
				1637	</div>
				1638
				1639	<!-- ======================================================================= -->
				1640	<div class="doc_subsection">
				1641	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1642	</div>
				1643
				1644	<div class="doc_text">
				1645
				1646	<p>Constant represents a base class for different types of constants. It
				1647	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1648	ConstantArray etc for representing the various types of Constants.</p>
				1649
				1650	</div>
				1651
				1652	<!-- _______________________________________________________________________ -->
				1653	<div class="doc_subsubsection">
				1654	<a name="m_Value">Important Public Methods</a>
				1655	</div>
				1656
				1657	<div class="doc_text">
				1658
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1659	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1660	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a
				1661	ConstantExpr
				1662	<hr> Important Subclasses of Constant
				1663	<p> </p>
				1664	<ul>
				1665	<li>ConstantSInt : This subclass of Constant represents a signed
				1666	integer constant.
				1667	<ul>
				1668	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1669	this constant. </li>
				1670	</ul>
				1671	</li>
				1672	<li>ConstantUInt : This class represents an unsigned integer.
				1673	<ul>
				1674	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value
				1675	of this constant. </li>
				1676	</ul>
				1677	</li>
				1678	<li>ConstantFP : This class represents a floating point constant.
				1679	<ul>
				1680	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1681	this constant. </li>
				1682	</ul>
				1683	</li>
				1684	<li>ConstantBool : This represents a boolean constant.
				1685	<ul>
				1686	<li><tt>bool getValue() const</tt>: Returns the underlying value of
				1687	this constant. </li>
				1688	</ul>
				1689	</li>
				1690	<li>ConstantArray : This represents a constant array.
				1691	<ul>
				1692	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1693	Returns a Vecotr of component constants that makeup this array. </li>
				1694	</ul>
				1695	</li>
				1696	<li>ConstantStruct : This represents a constant struct.
				1697	<ul>
				1698	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1699	Returns a Vecotr of component constants that makeup this array. </li>
				1700	</ul>
				1701	</li>
				1702	<li>ConstantPointerRef : This represents a constant pointer value
				1703	that is initialized to point to a global value, which lies at a
				1704	constant fixed address.
				1705	<ul>
				1706	<li><tt>GlobalValue *getValue()</tt>: Returns the global
				1707	value to which this pointer is pointing to. </li>
				1708	</ul>
				1709	</li>
				1710	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1711	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1712	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1713
				1714	</div>
				1715
				1716	<!-- ======================================================================= -->
				1717	<div class="doc_subsection">
				1718	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1719	</div>
				1720
				1721	<div class="doc_text">
				1722
				1723	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1724	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1725	types are instances of subclasses of type like FunctionType, ArrayType
				1726	etc. DerivedType is the interface for all such dervied types including
				1727	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1728	be recursive (StructType). There exists exactly one instance of any type
				1729	structure at a time. This allows using pointer equality of Type *s for comparing
				1730	types.</p>
				1731
				1732	</div>
				1733
				1734	<!-- _______________________________________________________________________ -->
				1735	<div class="doc_subsubsection">
				1736	<a name="m_Value">Important Public Methods</a>
				1737	</div>
				1738
				1739	<div class="doc_text">
				1740
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1741	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1742
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1743	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1744	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1745	not true for Float and Double. </li>
				1746
				1747	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1748	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1749	return false as they do with isSigned. This returns true for UByteTy,
				1750	UShortTy, UIntTy, and ULongTy. </li>
				1751
				1752	<li><tt>bool isInteger() const</tt>: Equilivent to isSigned() \|\| isUnsigned(),
				1753	but with only a single virtual function invocation.</li>
				1754
				1755	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1756	type, which is either Bool type or one of the Integer types.</li>
				1757
				1758	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1759	floating point types.</li>
				1760
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1761	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1762	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]	1763	example, uint to int or one pointer type to another.</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1764
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	1765	<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1766	<p>Derived Types</p>
				1767
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1768	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1769	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1770	<ul>
				1771	<li><tt>const Type * getElementType() const</tt>: Returns the type of
				1772	each of the elements in the sequential type. </li>
				1773	</ul>
				1774	</li>
				1775	<li>ArrayType : This is a subclass of SequentialType and defines
				1776	interface for array types.
				1777	<ul>
				1778	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1779	elements in the array. </li>
				1780	</ul>
				1781	</li>
				1782	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1783	<li>StructType : subclass of DerivedTypes for struct types </li>
				1784	<li>FunctionType : subclass of DerivedTypes for function types.
				1785	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1786	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1787	function</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1788	<li><tt> const Type * getReturnType() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1789	return type of the function.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1790	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1791	the type of the ith parameter.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1792	<li><tt> const unsigned getNumParams() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1793	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1794	</ul>
				1795	</li>
				1796	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1797	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1798	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1799
				1800	</div>
				1801
				1802	<!-- ======================================================================= -->
				1803	<div class="doc_subsection">
				1804	<a name="Argument">The <tt>Argument</tt> class</a>
				1805	</div>
				1806
				1807	<div class="doc_text">
				1808
				1809	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1810	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1811	arguments. An argument has a pointer to the parent Function.</p>
				1812
				1813	</div>
				1814
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1815	<!-- ======================================================================= -->
				1816	<div class="doc_subsection">
				1817	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1818	</div>
				1819	<div class="doc_text">
				1820	<p>This class provides a symbol table that the
				1821	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1822	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1823	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1824	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1825	type. It hides the data it contains and provides access to it through a
				1826	controlled interface.</p>
				1827
				1828	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1829	structure of the information it holds. The class contains two
				1830	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1831	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1832	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1833	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1834	however, are stored in a single dimension and accessed only by name.</p>
				1835
				1836	<p>The interface of this class provides three basic types of operations:
				1837	<ol>
				1838	<li><em>Accessors</em>. Accessors provide read-only access to information
				1839	such as finding a value for a name with the
				1840	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1841	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1842	<tt>SymbolTable</tt> with methods like
				1843	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1844	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1845	of the symbol table in well defined ways, such as the method
				1846	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1847	</ol>
				1848
				1849	<h3>Accessors</h3>
				1850	<dl>
				1851	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1852	</dt>
				1853	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1854	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1855	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1856
				1857	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1858	<dd>The <tt>lookupType</tt> method searches through the types for a
				1859	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1860	is not found, null is returned.</dd>
				1861
				1862	<dt><tt>bool hasTypes() const</tt>:</dt>
				1863	<dd>This function returns true if an entry has been made into the type
				1864	map.</dd>
				1865
				1866	<dt><tt>bool isEmpty() const</tt>:</dt>
				1867	<dd>This function returns true if both the value and types maps are
				1868	empty</dd>
				1869
				1870	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1871	<dd>This function returns the name of the Value provided or the empty
				1872	string if the Value is not in the symbol table.</dd>
				1873
				1874	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1875	<dd>This function returns the name of the Type provided or the empty
				1876	string if the Type is not in the symbol table.</dd>
				1877	</dl>
				1878
				1879	<h3>Mutators</h3>
				1880	<dl>
				1881	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1882	<dd>This method adds the provided value to the symbol table. The Value must
				1883	have both a name and a type which are extracted and used to place the value
				1884	in the correct type plane under the value's name.</dd>
				1885
				1886	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1887	<dd> Inserts a constant or type into the symbol table with the specified
				1888	name. There can be a many to one mapping between names and constants
				1889	or types.</dd>
				1890
				1891	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1892	<dd> Inserts a type into the symbol table with the specified name. There
				1893	can be a many-to-one mapping between names and types. This method
				1894	allows a type with an existing entry in the symbol table to get
				1895	a new name.</dd>
				1896
				1897	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1898	<dd> This method removes a named value from the symbol table. The
				1899	type and name of the Value are extracted from \p N and used to
				1900	lookup the Value in the correct type plane. If the Value is
				1901	not in the symbol table, this method silently ignores the
				1902	request.</dd>
				1903
				1904	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1905	<dd> This method removes a named type from the symbol table. The
				1906	name of the type is extracted from \P T and used to look up
				1907	the Type in the type map. If the Type is not in the symbol
				1908	table, this method silently ignores the request.</dd>
				1909
				1910	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1911	<dd> Remove a constant or type with the specified name from the
				1912	symbol table.</dd>
				1913
				1914	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1915	<dd> Remove a type with the specified name from the symbol table.
				1916	Returns the removed Type.</dd>
				1917
				1918	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1919	<dd> Removes a specific value from the symbol table.
				1920	Returns the removed value.</dd>
				1921
				1922	<dt><tt>bool strip()</tt>:</dt>
				1923	<dd> This method will strip the symbol table of its names leaving
				1924	the type and values. </dd>
				1925
				1926	<dt><tt>void clear()</tt>:</dt>
				1927	<dd>Empty the symbol table completely.</dd>
				1928	</dl>
				1929
				1930	<h3>Iteration</h3>
				1931	<p>The following functions describe three types of iterators you can obtain
				1932	the beginning or end of the sequence for both const and non-const. It is
				1933	important to keep track of the different kinds of iterators. There are
				1934	three idioms worth pointing out:</p>
				1935	<table class="doc_table">
				1936	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1937	<tr>
				1938	<td>Planes Of name/Value maps</td><td>PI</td>
				1939	<td><tt><pre>
				1940	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
				1941	PE = ST.plane_end(); PI != PE; ++PI ) {
				1942	PI->first // This is the Type* of the plane
				1943	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
				1944	</pre></tt></td>
				1945	</tr>
				1946	<tr>
				1947	<td>All name/Type Pairs</td><td>TI</td>
				1948	<td><tt><pre>
				1949	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1950	TE = ST.type_end(); TI != TE; ++TI )
				1951	TI->first // This is the name of the type
				1952	TI->second // This is the Type* value associated with the name
				1953	</pre></tt></td>
				1954	</tr>
				1955	<tr>
				1956	<td>name/Value pairs in a plane</td><td>VI</td>
				1957	<td><tt><pre>
				1958	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1959	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1960	VI->first // This is the name of the Value
				1961	VI->second // This is the Value* value associated with the name
				1962	</pre></tt></td>
				1963	</tr>
				1964	</table>
				1965	<p>Using the recommended iterator names and idioms will help you avoid
				1966	making mistakes. Of particular note, make sure that whenever you use
				1967	value_begin(SomeType) that you always compare the resulting iterator
				1968	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1969	will loop infinitely.</p>
				1970
				1971	<dl>
				1972
				1973	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1974	<dd>Get an iterator that starts at the beginning of the type planes.
				1975	The iterator will iterate over the Type/ValueMap pairs in the
				1976	type planes. </dd>
				1977
				1978	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1979	<dd>Get a const_iterator that starts at the beginning of the type
				1980	planes. The iterator will iterate over the Type/ValueMap pairs
				1981	in the type planes. </dd>
				1982
				1983	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1984	<dd>Get an 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>plane_const_iterator plane_end() const</tt>:</dt>
				1988	<dd>Get a const_iterator at the end of the type planes. This serves as
				1989	the marker for end of iteration over the type planes.</dd>
				1990
				1991	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				1992	<dd>Get an iterator that starts at the beginning of a type plane.
				1993	The iterator will iterate over the name/value pairs in the type plane.
				1994	Note: The type plane must already exist before using this.</dd>
				1995
				1996	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				1997	<dd>Get a const_iterator that starts at the beginning of a type plane.
				1998	The iterator will iterate over the name/value pairs in the type plane.
				1999	Note: The type plane must already exist before using this.</dd>
				2000
				2001	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				2002	<dd>Get an iterator to the end of a type plane. This serves as the marker
				2003	for end of iteration of the type plane.
				2004	Note: The type plane must already exist before using this.</dd>
				2005
				2006	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				2007	<dd>Get a const_iterator to the end of a type plane. This serves as the
				2008	marker for end of iteration of the type plane.
				2009	Note: the type plane must already exist before using this.</dd>
				2010
				2011	<dt><tt>type_iterator type_begin()</tt>:</dt>
				2012	<dd>Get an iterator to the start of the name/Type map.</dd>
				2013
				2014	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				2015	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				2016
				2017	<dt><tt>type_iterator type_end()</tt>:</dt>
				2018	<dd>Get an iterator to the end of the name/Type map. This serves as the
				2019	marker for end of iteration of the types.</dd>
				2020
				2021	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2022	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2023	as the marker for end of iteration of the types.</dd>
				2024
				2025	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2026	<dd>This method returns a plane_const_iterator for iteration over
				2027	the type planes starting at a specific plane, given by \p Ty.</dd>
				2028
				2029	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2030	<dd>This method returns a plane_iterator for iteration over the
				2031	type planes starting at a specific plane, given by \p Ty.</dd>
				2032
				2033	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2034	<dd>This method returns a ValueMap* for a specific type plane. This
				2035	interface is deprecated and may go away in the future.</dd>
				2036	</dl>
				2037	</div>
				2038
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2039	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2040	<hr>
				2041	<address>
				2042	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2043	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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				2045	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2046
				2047	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2048	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2049	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2050	Last modified: $Date$
				2051	</address>
				2052
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2053	</body>
				2054	</html>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	2055	<!-- vim: sw=2 noai
				2056	-->