Blame - docs/ProgrammersManual.html - platform/external/llvm

blob: 6fc0ec211256f2799e2d2f05f680a99f1ac0ee3f [file] [log] [blame]

Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
				2	"http://www.w3.org/TR/html4/strict.dtd">
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	3	<html>
				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	7	</head>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	8	<body>
				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	18	<li><a href="#stl">The C++ Standard Template Library</a></li>
				19	<!--
				20	<li>The <tt>-time-passes</tt> option</li>
				21	<li>How to use the LLVM Makefile system</li>
				22	<li>How to write a regression test</li>
Chris Lattner	61db465	2004-12-08 19:05:44 +0000	[diff] [blame]	23
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	24	-->
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	25	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	26	</li>
				27	<li><a href="#apis">Important and useful LLVM APIs</a>
				28	<ul>
				29	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				30	and <tt>dyn_cast<></tt> templates</a> </li>
				31	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				32	option</a>
				33	<ul>
				34	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				35	and the <tt>-debug-only</tt> option</a> </li>
				36	</ul>
				37	</li>
				38	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	39	option</a></li>
				40	<!--
				41	<li>The <tt>InstVisitor</tt> template
				42	<li>The general graph API
				43	-->
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	44	</ul>
				45	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	46	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	47	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	48	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				49	<ul>
				50	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				51	in a <tt>Function</tt></a> </li>
				52	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				53	in a <tt>BasicBlock</tt></a> </li>
				54	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				55	in a <tt>Function</tt></a> </li>
				56	<li><a href="#iterate_convert">Turning an iterator into a
				57	class pointer</a> </li>
				58	<li><a href="#iterate_complex">Finding call sites: a more
				59	complex example</a> </li>
				60	<li><a href="#calls_and_invokes">Treating calls and invokes
				61	the same way</a> </li>
				62	<li><a href="#iterate_chains">Iterating over def-use &
				63	use-def chains</a> </li>
				64	</ul>
				65	</li>
				66	<li><a href="#simplechanges">Making simple changes</a>
				67	<ul>
				68	<li><a href="#schanges_creating">Creating and inserting new
				69	<tt>Instruction</tt>s</a> </li>
				70	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				71	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				72	with another <tt>Value</tt></a> </li>
				73	</ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	74	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	75	<!--
				76	<li>Working with the Control Flow Graph
				77	<ul>
				78	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				79	<li>
				80	<li>
				81	</ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	82	-->
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	83	</ul>
				84	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	85	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	86	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	87	<li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	88	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	89	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	90	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	91	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
				92	<ul>
				93	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
				94	</ul>
				95	</li>
				96	<li><a href="#Module">The <tt>Module</tt> class</a></li>
				97	<li><a href="#Constant">The <tt>Constant</tt> class</a>
				98	<ul>
				99	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				100	<ul>
				101	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				102	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				103	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
				104	</ul>
				105	</li>
				106	</ul>
				107	</li>
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	108	</ul>
				109	</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	110	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	111	<li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	112	</ul>
				113	</li>
				114	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	115	</li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	116	<li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
				117	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
				118	<ul>
				119	<li>Creating, inserting, moving and deleting from LLVM lists </li>
				120	</ul>
				121	</li>
				122	<li>Important iterator invalidation semantics to be aware of.</li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	123	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	124
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	125	<div class="doc_author">
				126	<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner	94c4359	2004-05-26 16:52:55 +0000	[diff] [blame]	127	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
				128	<a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
				129	<a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	130	</div>
				131
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	132	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	133	<div class="doc_section">
				134	<a name="introduction">Introduction </a>
				135	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	136	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	137
				138	<div class="doc_text">
				139
				140	<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]	141	interfaces available in the LLVM source-base. This manual is not
				142	intended to explain what LLVM is, how it works, and what LLVM code looks
				143	like. It assumes that you know the basics of LLVM and are interested
				144	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	145	code.</p>
				146
				147	<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]	148	way in the continuously growing source code that makes up the LLVM
				149	infrastructure. Note that this manual is not intended to serve as a
				150	replacement for reading the source code, so if you think there should be
				151	a method in one of these classes to do something, but it's not listed,
				152	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				153	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	154
				155	<p>The first section of this document describes general information that is
				156	useful to know when working in the LLVM infrastructure, and the second describes
				157	the Core LLVM classes. In the future this manual will be extended with
				158	information describing how to use extension libraries, such as dominator
				159	information, CFG traversal routines, and useful utilities like the <tt><a
				160	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				161
				162	</div>
				163
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	164	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	165	<div class="doc_section">
				166	<a name="general">General Information</a>
				167	</div>
				168	<!-- *********************************************************************** -->
				169
				170	<div class="doc_text">
				171
				172	<p>This section contains general information that is useful if you are working
				173	in the LLVM source-base, but that isn't specific to any particular API.</p>
				174
				175	</div>
				176
				177	<!-- ======================================================================= -->
				178	<div class="doc_subsection">
				179	<a name="stl">The C++ Standard Template Library</a>
				180	</div>
				181
				182	<div class="doc_text">
				183
				184	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	185	perhaps much more than you are used to, or have seen before. Because of
				186	this, you might want to do a little background reading in the
				187	techniques used and capabilities of the library. There are many good
				188	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]	189	can get, so it will not be discussed in this document.</p>
				190
				191	<p>Here are some useful links:</p>
				192
				193	<ol>
				194
				195	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				196	reference</a> - an excellent reference for the STL and other parts of the
				197	standard C++ library.</li>
				198
				199	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Tanya Lattner	09cf73c	2004-06-22 04:24:55 +0000	[diff] [blame]	200	O'Reilly book in the making. It has a decent
				201	Standard Library
				202	Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	203	published.</li>
				204
				205	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				206	Questions</a></li>
				207
				208	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				209	Contains a useful <a
				210	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				211	STL</a>.</li>
				212
				213	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				214	Page</a></li>
				215
Tanya Lattner	79445ba	2004-12-08 18:34:56 +0000	[diff] [blame]	216	<li><a href="http://64.78.49.204/">
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	217	Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
				218	the book).</a></li>
				219
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	220	</ol>
				221
				222	<p>You are also encouraged to take a look at the <a
				223	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				224	to write maintainable code more than where to put your curly braces.</p>
				225
				226	</div>
				227
				228	<!-- ======================================================================= -->
				229	<div class="doc_subsection">
				230	<a name="stl">Other useful references</a>
				231	</div>
				232
				233	<div class="doc_text">
				234
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	235	<ol>
				236	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	237	Branch and Tag Primer</a></li>
Misha Brukman	a0f71e4	2004-06-18 18:39:00 +0000	[diff] [blame]	238	<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
				239	static and shared libraries across platforms</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	240	</ol>
				241
				242	</div>
				243
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	244	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	245	<div class="doc_section">
				246	<a name="apis">Important and useful LLVM APIs</a>
				247	</div>
				248	<!-- *********************************************************************** -->
				249
				250	<div class="doc_text">
				251
				252	<p>Here we highlight some LLVM APIs that are generally useful and good to
				253	know about when writing transformations.</p>
				254
				255	</div>
				256
				257	<!-- ======================================================================= -->
				258	<div class="doc_subsection">
				259	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				260	</div>
				261
				262	<div class="doc_text">
				263
				264	<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]	265	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				266	operator, but they don't have some drawbacks (primarily stemming from
				267	the fact that <tt>dynamic_cast<></tt> only works on classes that
				268	have a v-table). Because they are used so often, you must know what they
				269	do and how they work. All of these templates are defined in the <a
				270	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	271	file (note that you very rarely have to include this file directly).</p>
				272
				273	<dl>
				274	<dt><tt>isa<></tt>: </dt>
				275
				276	<dd>The <tt>isa<></tt> operator works exactly like the Java
				277	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				278	a reference or pointer points to an instance of the specified class. This can
				279	be very useful for constraint checking of various sorts (example below).</dd>
				280
				281	<dt><tt>cast<></tt>: </dt>
				282
				283	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				284	converts a pointer or reference from a base class to a derived cast, causing
				285	an assertion failure if it is not really an instance of the right type. This
				286	should be used in cases where you have some information that makes you believe
				287	that something is of the right type. An example of the <tt>isa<></tt>
				288	and <tt>cast<></tt> template is:
				289
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	290	<pre>
				291	static bool isLoopInvariant(const <a href="#Value">Value</a> V, const Loop L) {
				292	if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a href="#Argument">Argument</a>>(V) \|\| isa<<a href="#GlobalValue">GlobalValue</a>>(V))
				293	return true;
				294
				295	<i>// Otherwise, it must be an instruction...</i>
				296	return !L->contains(cast<<a href="#Instruction">Instruction</a>>(V)->getParent());
				297	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	298
				299	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				300	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				301	operator.</p>
				302
				303	</dd>
				304
				305	<dt><tt>dyn_cast<></tt>:</dt>
				306
				307	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				308	checks to see if the operand is of the specified type, and if so, returns a
				309	pointer to it (this operator does not work with references). If the operand is
				310	not of the correct type, a null pointer is returned. Thus, this works very
				311	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				312	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				313	in an <tt>if</tt> statement or some other flow control statement like this:
				314
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	315	<pre>
				316	if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a href="#AllocationInst">AllocationInst</a>>(Val)) {
				317	...
				318	}
				319	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	320
				321	<p> This form of the <tt>if</tt> statement effectively combines together a
				322	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				323	statement, which is very convenient.</p>
				324
				325	<p> Another common example is:</p>
				326
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	327	<pre>
				328	<i>// Loop over all of the phi nodes in a basic block</i>
				329	BasicBlock::iterator BBI = BB->begin();
				330	for (; <a href="#PhiNode">PHINode</a> *PN = dyn_cast<<a href="#PHINode">PHINode</a>>(BBI); ++BBI)
				331	std::cerr << *PN;
				332	</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	333
				334	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				335	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				336	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				337	check for lots of different variants of classes. If you find yourself
				338	wanting to do this, it is much cleaner and more efficient to use the
				339	InstVisitor class to dispatch over the instruction type directly.</p>
				340
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	341	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	342
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	343	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	344
				345	<dd>The <tt>cast_or_null<></tt> operator works just like the
				346	<tt>cast<></tt> operator, except that it allows for a null pointer as
				347	an argument (which it then propagates). This can sometimes be useful,
				348	allowing you to combine several null checks into one.</dd>
				349
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	350	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	351
				352	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				353	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				354	as an argument (which it then propagates). This can sometimes be useful,
				355	allowing you to combine several null checks into one.</dd>
				356
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	357	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	358
				359	<p>These five templates can be used with any classes, whether they have a
				360	v-table or not. To add support for these templates, you simply need to add
				361	<tt>classof</tt> static methods to the class you are interested casting
				362	to. Describing this is currently outside the scope of this document, but there
				363	are lots of examples in the LLVM source base.</p>
				364
				365	</div>
				366
				367	<!-- ======================================================================= -->
				368	<div class="doc_subsection">
				369	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				370	</div>
				371
				372	<div class="doc_text">
				373
				374	<p>Often when working on your pass you will put a bunch of debugging printouts
				375	and other code into your pass. After you get it working, you want to remove
				376	it... but you may need it again in the future (to work out new bugs that you run
				377	across).</p>
				378
				379	<p> Naturally, because of this, you don't want to delete the debug printouts,
				380	but you don't want them to always be noisy. A standard compromise is to comment
				381	them out, allowing you to enable them if you need them in the future.</p>
				382
				383	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				384	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				385	this problem. Basically, you can put arbitrary code into the argument of the
				386	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				387	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				388
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	389	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	390
				391	<p>Then you can run your pass like this:</p>
				392
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	393	<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]	394
				395	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				396	to not have to create "yet another" command line option for the debug output for
				397	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				398	so they do not cause a performance impact at all (for the same reason, they
				399	should also not contain side-effects!).</p>
				400
				401	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				402	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				403	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				404	program hasn't been started yet, you can always just run it with
				405	<tt>-debug</tt>.</p>
				406
				407	</div>
				408
				409	<!-- _______________________________________________________________________ -->
				410	<div class="doc_subsubsection">
				411	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				412	the <tt>-debug-only</tt> option</a>
				413	</div>
				414
				415	<div class="doc_text">
				416
				417	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				418	just turns on <b>too much</b> information (such as when working on the code
				419	generator). If you want to enable debug information with more fine-grained
				420	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				421	option as follows:</p>
				422
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	423	<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]	424
				425	<p>Then you can run your pass like this:</p>
				426
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	427	<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]	428
				429	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				430	a file, to specify the debug type for the entire module (if you do this before
				431	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				432	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				433	"bar", because there is no system in place to ensure that names do not
				434	conflict. If two different modules use the same string, they will all be turned
				435	on when the name is specified. This allows, for example, all debug information
				436	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	437	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	438
				439	</div>
				440
				441	<!-- ======================================================================= -->
				442	<div class="doc_subsection">
				443	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				444	option</a>
				445	</div>
				446
				447	<div class="doc_text">
				448
				449	<p>The "<tt><a
				450	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				451	provides a template named <tt>Statistic</tt> that is used as a unified way to
				452	keep track of what the LLVM compiler is doing and how effective various
				453	optimizations are. It is useful to see what optimizations are contributing to
				454	making a particular program run faster.</p>
				455
				456	<p>Often you may run your pass on some big program, and you're interested to see
				457	how many times it makes a certain transformation. Although you can do this with
				458	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				459	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				460	keep track of this information, and the calculated information is presented in a
				461	uniform manner with the rest of the passes being executed.</p>
				462
				463	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				464	it are as follows:</p>
				465
				466	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	467	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	468	<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]	469
				470	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				471	but if you do not specify a template argument, it defaults to acting like
				472	an unsigned int counter (this is usually what you want).</p></li>
				473
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	474	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	475	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	476	</li>
				477	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	478
				479	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				480	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				481
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	482	<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]	483
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	484	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				485	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	486
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	487	<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]	488
				489	<p>Obviously, with so many optimizations, having a unified framework for this
				490	stuff is very nice. Making your pass fit well into the framework makes it more
				491	maintainable and useful.</p>
				492
				493	</div>
				494
				495	<!-- *********************************************************************** -->
				496	<div class="doc_section">
				497	<a name="common">Helpful Hints for Common Operations</a>
				498	</div>
				499	<!-- *********************************************************************** -->
				500
				501	<div class="doc_text">
				502
				503	<p>This section describes how to perform some very simple transformations of
				504	LLVM code. This is meant to give examples of common idioms used, showing the
				505	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				506	you should also read about the main classes that you will be working with. The
				507	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				508	and descriptions of the main classes that you should know about.</p>
				509
				510	</div>
				511
				512	<!-- NOTE: this section should be heavy on example code -->
				513	<!-- ======================================================================= -->
				514	<div class="doc_subsection">
				515	<a name="inspection">Basic Inspection and Traversal Routines</a>
				516	</div>
				517
				518	<div class="doc_text">
				519
				520	<p>The LLVM compiler infrastructure have many different data structures that may
				521	be traversed. Following the example of the C++ standard template library, the
				522	techniques used to traverse these various data structures are all basically the
				523	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				524	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				525	function returns an iterator pointing to one past the last valid element of the
				526	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				527	between the two operations.</p>
				528
				529	<p>Because the pattern for iteration is common across many different aspects of
				530	the program representation, the standard template library algorithms may be used
				531	on them, and it is easier to remember how to iterate. First we show a few common
				532	examples of the data structures that need to be traversed. Other data
				533	structures are traversed in very similar ways.</p>
				534
				535	</div>
				536
				537	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	538	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	539	<a name="iterate_function">Iterating over the </a><a
				540	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				541	href="#Function"><tt>Function</tt></a>
				542	</div>
				543
				544	<div class="doc_text">
				545
				546	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				547	transform in some way; in particular, you'd like to manipulate its
				548	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				549	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				550	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				551	<tt>Instruction</tt>s it contains:</p>
				552
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	553	<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]	554
				555	<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]	556	invoking member functions of the <tt>Instruction</tt> class. This is
				557	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	558	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	559	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				560
				561	</div>
				562
				563	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	564	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	565	<a name="iterate_basicblock">Iterating over the </a><a
				566	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				567	href="#BasicBlock"><tt>BasicBlock</tt></a>
				568	</div>
				569
				570	<div class="doc_text">
				571
				572	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				573	easy to iterate over the individual instructions that make up
				574	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				575	a <tt>BasicBlock</tt>:</p>
				576
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	577	<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]	578
				579	<p>However, this isn't really the best way to print out the contents of a
				580	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				581	anything you'll care about, you could have just invoked the print routine on the
				582	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				583
				584	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				585	it will print out the contents of the pointer, instead of the pointer value you
				586	might expect. This is a deprecated interface that will be removed in the
				587	future, so it's best not to depend on it. To print out the pointer value for
				588	now, you must cast to <tt>void*</tt>.</p>
				589
				590	</div>
				591
				592	<!-- _______________________________________________________________________ -->
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	593	<div class="doc_subsubsection">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	594	<a name="iterate_institer">Iterating over the </a><a
				595	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				596	href="#Function"><tt>Function</tt></a>
				597	</div>
				598
				599	<div class="doc_text">
				600
				601	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				602	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				603	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				604	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				605	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]	606	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]	607
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	608	<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]	609	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				610	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	611	initialize a worklist to contain all instructions in a <tt>Function</tt>
				612	F, all you would need to do is something like:
				613	<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]	614
				615	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				616	<tt>Function</tt> pointed to by F.</p>
				617
				618	</div>
				619
				620	<!-- _______________________________________________________________________ -->
				621	<div class="doc_subsubsection">
				622	<a name="iterate_convert">Turning an iterator into a class pointer (and
				623	vice-versa)</a>
				624	</div>
				625
				626	<div class="doc_text">
				627
				628	<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]	629	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]	630	a reference or a pointer from an iterator is very straight-forward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	631	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]	632	is a <tt>BasicBlock::const_iterator</tt>:</p>
				633
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	634	<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]	635
				636	<p>However, the iterators you'll be working with in the LLVM framework are
				637	special: they will automatically convert to a ptr-to-instance type whenever they
				638	need to. Instead of dereferencing the iterator and then taking the address of
				639	the result, you can simply assign the iterator to the proper pointer type and
				640	you get the dereference and address-of operation as a result of the assignment
				641	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				642	the last line of the last example,</p>
				643
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	644	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	645
				646	<p>is semantically equivalent to</p>
				647
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	648	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	649
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	650	<p>It's also possible to turn a class pointer into the corresponding iterator,
				651	and this is a constant time operation (very efficient). The following code
				652	snippet illustrates use of the conversion constructors provided by LLVM
				653	iterators. By using these, you can explicitly grab the iterator of something
				654	without actually obtaining it via iteration over some structure:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	655
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	656	<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]	657
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	658	</div>
				659
				660	<!--_______________________________________________________________________-->
				661	<div class="doc_subsubsection">
				662	<a name="iterate_complex">Finding call sites: a slightly more complex
				663	example</a>
				664	</div>
				665
				666	<div class="doc_text">
				667
				668	<p>Say that you're writing a FunctionPass and would like to count all the
				669	locations in the entire module (that is, across every <tt>Function</tt>) where a
				670	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				671	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]	672	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]	673	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				674	is what we want to do:</p>
				675
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	676	<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]	677
				678	<p>And the actual code is (remember, since we're writing a
				679	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				680	override the <tt>runOnFunction</tt> method...):</p>
				681
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	682	<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
				683	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				684	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]	685
				686	</div>
				687
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	688	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	689	<div class="doc_subsubsection">
				690	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				691	</div>
				692
				693	<div class="doc_text">
				694
				695	<p>You may have noticed that the previous example was a bit oversimplified in
				696	that it did not deal with call sites generated by 'invoke' instructions. In
				697	this, and in other situations, you may find that you want to treat
				698	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				699	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				700	less closely-related things. For these cases, LLVM provides a handy wrapper
				701	class called <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	702	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]	703	It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
				704	methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	705	<tt>InvokeInst</tt>s.</p>
				706
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	707	<p>This class has "value semantics": it should be passed by value, not by
				708	reference and it should not be dynamically allocated or deallocated using
				709	<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
				710	assignable and constructable, with costs equivalents to that of a bare pointer.
				711	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]	712
				713	</div>
				714
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	715	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	716	<div class="doc_subsubsection">
				717	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				718	</div>
				719
				720	<div class="doc_text">
				721
				722	<p>Frequently, we might have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	723	href="/doxygen/structllvm_1_1Value.html">Value Class</a> and we want to
				724	determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
				725	<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
				726	For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
				727	particular function <tt>foo</tt>. Finding all of the instructions that
				728	<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
				729	of <tt>F</tt>:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	730
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	731	<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]	732
				733	<p>Alternately, it's common to have an instance of the <a
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	734	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]	735	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				736	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				737	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				738	all of the values that a particular instruction uses (that is, the operands of
				739	the particular <tt>Instruction</tt>):</p>
				740
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	741	<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]	742
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	743	<!--
				744	def-use chains ("finding all users of"): Value::use_begin/use_end
				745	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]	746	-->
				747
				748	</div>
				749
				750	<!-- ======================================================================= -->
				751	<div class="doc_subsection">
				752	<a name="simplechanges">Making simple changes</a>
				753	</div>
				754
				755	<div class="doc_text">
				756
				757	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	758	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	759	transformations, it's fairly common to manipulate the contents of basic
				760	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	761	and gives example code.</p>
				762
				763	</div>
				764
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	765	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	766	<div class="doc_subsubsection">
				767	<a name="schanges_creating">Creating and inserting new
				768	<tt>Instruction</tt>s</a>
				769	</div>
				770
				771	<div class="doc_text">
				772
				773	<p><i>Instantiating Instructions</i></p>
				774
Chris Lattner	69bf8a9	2004-05-23 21:06:58 +0000	[diff] [blame]	775	<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]	776	constructor for the kind of instruction to instantiate and provide the necessary
				777	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				778	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				779
				780	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				781
				782	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				783	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				784	subclass is likely to have varying default parameters which change the semantics
				785	of the instruction, so refer to the <a
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	786	href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	787	Instruction</a> that you're interested in instantiating.</p>
				788
				789	<p><i>Naming values</i></p>
				790
				791	<p>It is very useful to name the values of instructions when you're able to, as
				792	this facilitates the debugging of your transformations. If you end up looking
				793	at generated LLVM machine code, you definitely want to have logical names
				794	associated with the results of instructions! By supplying a value for the
				795	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				796	associate a logical name with the result of the instruction's execution at
				797	runtime. For example, say that I'm writing a transformation that dynamically
				798	allocates space for an integer on the stack, and that integer is going to be
				799	used as some kind of index by some other code. To accomplish this, I place an
				800	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				801	<tt>Function</tt>, and I'm intending to use it within the same
				802	<tt>Function</tt>. I might do:</p>
				803
				804	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				805
				806	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				807	execution value, which is a pointer to an integer on the runtime stack.</p>
				808
				809	<p><i>Inserting instructions</i></p>
				810
				811	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				812	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				813
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	814	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	815	<li>Insertion into an explicit instruction list
				816
				817	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				818	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				819	before <tt>*pi</tt>, we do the following: </p>
				820
Alkis Evlogimenos	9a5dc4f	2004-05-27 00:57:51 +0000	[diff] [blame]	821	<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>
				822
				823	<p>Appending to the end of a <tt>BasicBlock</tt> is so common that
				824	the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
				825	classes provide constructors which take a pointer to a
				826	<tt>BasicBlock</tt> to be appended to. For example code that
				827	looked like: </p>
				828
				829	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(...);<br> pb->getInstList().push_back(newInst); // appends newInst to pb<br></pre>
				830
				831	<p>becomes: </p>
				832
				833	<pre> BasicBlock pb = ...;<br> Instruction newInst = new Instruction(..., pb);<br></pre>
				834
				835	<p>which is much cleaner, especially if you are creating
				836	long instruction streams.</p></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	837
				838	<li>Insertion into an implicit instruction list
				839
				840	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				841	are implicitly associated with an existing instruction list: the instruction
				842	list of the enclosing basic block. Thus, we could have accomplished the same
				843	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				844	</p>
				845
				846	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				847
				848	<p>In fact, this sequence of steps occurs so frequently that the
				849	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				850	constructors which take (as a default parameter) a pointer to an
				851	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				852	precede. That is, <tt>Instruction</tt> constructors are capable of
				853	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				854	provided instruction, immediately before that instruction. Using an
				855	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				856	parameter, the above code becomes:</p>
				857
				858	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				859
				860	<p>which is much cleaner, especially if you're creating a lot of
				861	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				862	</ul>
				863
				864	</div>
				865
				866	<!--_______________________________________________________________________-->
				867	<div class="doc_subsubsection">
				868	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				869	</div>
				870
				871	<div class="doc_text">
				872
				873	<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]	874	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	875	you must have a pointer to the instruction that you wish to delete. Second, you
				876	need to obtain the pointer to that instruction's basic block. You use the
				877	pointer to the basic block to get its list of instructions and then use the
				878	erase function to remove your instruction. For example:</p>
				879
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	880	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				881	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]	882
				883	</div>
				884
				885	<!--_______________________________________________________________________-->
				886	<div class="doc_subsubsection">
				887	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				888	<tt>Value</tt></a>
				889	</div>
				890
				891	<div class="doc_text">
				892
				893	<p><i>Replacing individual instructions</i></p>
				894
				895	<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]	896	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	897	and <tt>ReplaceInstWithInst</tt>.</p>
				898
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	899	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	900
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	901	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	902	<li><tt>ReplaceInstWithValue</tt>
				903
				904	<p>This function replaces all uses (within a basic block) of a given
				905	instruction with a value, and then removes the original instruction. The
				906	following example illustrates the replacement of the result of a particular
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame^]	907	<tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	908	pointer to an integer.</p>
				909
				910	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				911
				912	<li><tt>ReplaceInstWithInst</tt>
				913
				914	<p>This function replaces a particular instruction with another
				915	instruction. The following example illustrates the replacement of one
				916	<tt>AllocaInst</tt> with another.</p>
				917
				918	<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]	919	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	920
				921	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				922
				923	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				924	<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]	925	doxygen documentation for the <a href="/doxygen/structllvm_1_1Value.html">Value Class</a>
				926	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]	927	information.</p>
				928
				929	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				930	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				931	ReplaceInstWithValue, ReplaceInstWithInst -->
				932
				933	</div>
				934
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	935	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	936	<div class="doc_section">
				937	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				938	</div>
				939	<!-- *********************************************************************** -->
				940
				941	<div class="doc_text">
				942
				943	<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]	944	being inspected or transformed. The core LLVM classes are defined in
				945	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	946	the <tt>lib/VMCore</tt> directory.</p>
				947
				948	</div>
				949
				950	<!-- ======================================================================= -->
				951	<div class="doc_subsection">
				952	<a name="Value">The <tt>Value</tt> class</a>
				953	</div>
				954
				955	<div>
				956
				957	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				958	<br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	959	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]	960
				961	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				962	base. It represents a typed value that may be used (among other things) as an
				963	operand to an instruction. There are many different types of <tt>Value</tt>s,
				964	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				965	href="#Argument"><tt>Argument</tt></a>s. Even <a
				966	href="#Instruction"><tt>Instruction</tt></a>s and <a
				967	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				968
				969	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				970	for a program. For example, an incoming argument to a function (represented
				971	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				972	every instruction in the function that references the argument. To keep track
				973	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				974	href="#User"><tt>User</tt></a>s that is using it (the <a
				975	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				976	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				977	def-use information in the program, and is accessible through the <tt>use_</tt>*
				978	methods, shown below.</p>
				979
				980	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				981	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				982	method. In addition, all LLVM values can be named. The "name" of the
				983	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				984
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	985	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	986
				987	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				988	that the name of any value may be missing (an empty string), so names should
				989	<b>ONLY</b> be used for debugging (making the source code easier to read,
				990	debugging printouts), they should not be used to keep track of values or map
				991	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				992	<tt>Value</tt> itself instead.</p>
				993
				994	<p>One important aspect of LLVM is that there is no distinction between an SSA
				995	variable and the operation that produces it. Because of this, any reference to
				996	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]	997	argument, for example) is represented as a direct pointer to the instance of
				998	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	999	represents this value. Although this may take some getting used to, it
				1000	simplifies the representation and makes it easier to manipulate.</p>
				1001
				1002	</div>
				1003
				1004	<!-- _______________________________________________________________________ -->
				1005	<div class="doc_subsubsection">
				1006	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				1007	</div>
				1008
				1009	<div class="doc_text">
				1010
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1011	<ul>
				1012	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				1013	use-list<br>
				1014	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				1015	the use-list<br>
				1016	<tt>unsigned use_size()</tt> - Returns the number of users of the
				1017	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1018	<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]	1019	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1020	the use-list.<br>
				1021	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1022	use-list.<br>
				1023	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1024	element in the list.
				1025	<p> These methods are the interface to access the def-use
				1026	information in LLVM. As with all other iterators in LLVM, the naming
				1027	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]	1028	</li>
				1029	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1030	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1031	</li>
				1032	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1033	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1034	<tt>void setName(const std::string &Name)</tt>
				1035	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1036	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1037	</li>
				1038	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1039
				1040	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1041	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1042	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1043	produces a constant value (for example through constant folding), you can
				1044	replace all uses of the instruction with the constant like this:</p>
				1045
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1046	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1047	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1048
				1049	</div>
				1050
				1051	<!-- ======================================================================= -->
				1052	<div class="doc_subsection">
				1053	<a name="User">The <tt>User</tt> class</a>
				1054	</div>
				1055
				1056	<div class="doc_text">
				1057
				1058	<p>
				1059	<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]	1060	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]	1061	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1062
				1063	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1064	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1065	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1066	referring to. The <tt>User</tt> class itself is a subclass of
				1067	<tt>Value</tt>.</p>
				1068
				1069	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1070	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1071	Single Assignment (SSA) form, there can only be one definition referred to,
				1072	allowing this direct connection. This connection provides the use-def
				1073	information in LLVM.</p>
				1074
				1075	</div>
				1076
				1077	<!-- _______________________________________________________________________ -->
				1078	<div class="doc_subsubsection">
				1079	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1080	</div>
				1081
				1082	<div class="doc_text">
				1083
				1084	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1085	an index access interface and through an iterator based interface.</p>
				1086
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1087	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1088	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1089	<tt>unsigned getNumOperands()</tt>
				1090	<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]	1091	convenient form for direct access.</p></li>
				1092
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1093	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1094	list<br>
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame^]	1095	<tt>op_iterator op_begin()</tt> - Get an iterator to the start of
				1096	the operand list.<br>
				1097	<tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1098	operand list.
				1099	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1100	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1101	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1102
				1103	</div>
				1104
				1105	<!-- ======================================================================= -->
				1106	<div class="doc_subsection">
				1107	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1108	</div>
				1109
				1110	<div class="doc_text">
				1111
				1112	<p><tt>#include "</tt><tt><a
				1113	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1114	doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1115	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1116	href="#Value"><tt>Value</tt></a></p>
				1117
				1118	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1119	instructions. It provides only a few methods, but is a very commonly used
				1120	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1121	opcode (instruction type) and the parent <a
				1122	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1123	into. To represent a specific type of instruction, one of many subclasses of
				1124	<tt>Instruction</tt> are used.</p>
				1125
				1126	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1127	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1128	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1129	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1130	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1131	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1132	file contains some meta-data about the various different types of instructions
				1133	in LLVM. It describes the enum values that are used as opcodes (for example
				1134	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1135	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1136	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1137	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1138	this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1139	<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1140
				1141	</div>
				1142
				1143	<!-- _______________________________________________________________________ -->
				1144	<div class="doc_subsubsection">
				1145	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1146	class</a>
				1147	</div>
				1148
				1149	<div class="doc_text">
				1150
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1151	<ul>
				1152	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1153	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1154	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1155	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1156	<p>Returns true if the instruction writes to memory, i.e. it is a
				1157	<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]	1158	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1159	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1160	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1161	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1162	in all ways to the original except that the instruction has no parent
				1163	(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]	1164	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1165	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1166
				1167	</div>
				1168
				1169	<!-- ======================================================================= -->
				1170	<div class="doc_subsection">
				1171	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1172	</div>
				1173
				1174	<div class="doc_text">
				1175
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1176	<p><tt>#include "<a
				1177	href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
				1178	doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
				1179	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1180	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1181
				1182	<p>This class represents a single entry multiple exit section of the code,
				1183	commonly known as a basic block by the compiler community. The
				1184	<tt>BasicBlock</tt> class maintains a list of <a
				1185	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1186	Matching the language definition, the last element of this list of instructions
				1187	is always a terminator instruction (a subclass of the <a
				1188	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1189
				1190	<p>In addition to tracking the list of instructions that make up the block, the
				1191	<tt>BasicBlock</tt> class also keeps track of the <a
				1192	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1193
				1194	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1195	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1196	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1197	<tt>label</tt>.</p>
				1198
				1199	</div>
				1200
				1201	<!-- _______________________________________________________________________ -->
				1202	<div class="doc_subsubsection">
				1203	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1204	class</a>
				1205	</div>
				1206
				1207	<div class="doc_text">
				1208
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1209	<ul>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1210
				1211	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1212	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	b0e7e45	2004-10-29 04:33:19 +0000	[diff] [blame]	1213
				1214	<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
				1215	insertion into a function. The constructor optionally takes a name for the new
				1216	block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
				1217	the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
				1218	automatically inserted at the end of the specified <a
				1219	href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
				1220	manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
				1221
				1222	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
				1223	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
				1224	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1225	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt> -
				1226	STL-style functions for accessing the instruction list.
				1227
				1228	<p>These methods and typedefs are forwarding functions that have the same
				1229	semantics as the standard library methods of the same names. These methods
				1230	expose the underlying instruction list of a basic block in a way that is easy to
				1231	manipulate. To get the full complement of container operations (including
				1232	operations to update the list), you must use the <tt>getInstList()</tt>
				1233	method.</p></li>
				1234
				1235	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1236
				1237	<p>This method is used to get access to the underlying container that actually
				1238	holds the Instructions. This method must be used when there isn't a forwarding
				1239	function in the <tt>BasicBlock</tt> class for the operation that you would like
				1240	to perform. Because there are no forwarding functions for "updating"
				1241	operations, you need to use this if you want to update the contents of a
				1242	<tt>BasicBlock</tt>.</p></li>
				1243
				1244	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1245
				1246	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
				1247	embedded into, or a null pointer if it is homeless.</p></li>
				1248
				1249	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1250
				1251	<p> Returns a pointer to the terminator instruction that appears at the end of
				1252	the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
				1253	instruction in the block is not a terminator, then a null pointer is
				1254	returned.</p></li>
				1255
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1256	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1257
				1258	</div>
				1259
				1260	<!-- ======================================================================= -->
				1261	<div class="doc_subsection">
				1262	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1263	</div>
				1264
				1265	<div class="doc_text">
				1266
				1267	<p><tt>#include "<a
				1268	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman	384047f	2004-06-03 23:29:12 +0000	[diff] [blame]	1269	doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
				1270	Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1271	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1272	href="#Value"><tt>Value</tt></a></p>
				1273
				1274	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1275	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1276	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1277	Because they are visible at global scope, they are also subject to linking with
				1278	other globals defined in different translation units. To control the linking
				1279	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1280	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1281	defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1282
				1283	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1284	<tt>static</tt> in C), it is not visible to code outside the current translation
				1285	unit, and does not participate in linking. If it has external linkage, it is
				1286	visible to external code, and does participate in linking. In addition to
				1287	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1288	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1289
				1290	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1291	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1292	global is always a pointer to its contents. It is important to remember this
				1293	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1294	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1295	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1296	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1297	the address of the first element of this array and the value of the
				1298	<tt>GlobalVariable</tt> are the same, they have different types. The
				1299	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1300	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1301	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1302	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1303	Language Reference Manual</a>.</p>
				1304
				1305	</div>
				1306
				1307	<!-- _______________________________________________________________________ -->
				1308	<div class="doc_subsubsection">
				1309	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1310	class</a>
				1311	</div>
				1312
				1313	<div class="doc_text">
				1314
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1315	<ul>
				1316	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1317	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1318	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1319	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1320	<p> </p>
				1321	</li>
				1322	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1323	<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]	1324	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1325	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1326
				1327	</div>
				1328
				1329	<!-- ======================================================================= -->
				1330	<div class="doc_subsection">
				1331	<a name="Function">The <tt>Function</tt> class</a>
				1332	</div>
				1333
				1334	<div class="doc_text">
				1335
				1336	<p><tt>#include "<a
				1337	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman	31ca1de	2004-06-03 23:35:54 +0000	[diff] [blame]	1338	info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
				1339	Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1340	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1341
				1342	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1343	actually one of the more complex classes in the LLVM heirarchy because it must
				1344	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1345	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1346	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1347	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1348
				1349	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1350	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1351	ordering of the blocks in the function, which indicate how the code will be
				1352	layed out by the backend. Additionally, the first <a
				1353	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1354	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1355	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1356	nodes from a single <tt>Function</tt>. If the <a
				1357	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1358	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1359	function hasn't been linked in yet.</p>
				1360
				1361	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1362	<tt>Function</tt> class also keeps track of the list of formal <a
				1363	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1364	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1365	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1366	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1367
				1368	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1369	LLVM feature that is only used when you have to look up a value by name. Aside
				1370	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1371	internally to make sure that there are not conflicts between the names of <a
				1372	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1373	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1374	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1375
Reid Spencer	8b2da7a	2004-07-18 13:10:31 +0000	[diff] [blame]	1376	<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
				1377	and therefore also a <a href="#Constant">Constant</a>. The value of the function
				1378	is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1379	</div>
				1380
				1381	<!-- _______________________________________________________________________ -->
				1382	<div class="doc_subsubsection">
				1383	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1384	class</a>
				1385	</div>
				1386
				1387	<div class="doc_text">
				1388
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1389	<ul>
				1390	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1391	Ty, LinkageTypes Linkage, const std::string &N = "", Module Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1392
				1393	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1394	the the program. The constructor must specify the type of the function to
Chris Lattner	ac479e5	2004-08-04 05:10:48 +0000	[diff] [blame]	1395	create and what type of linkage the function should have. The <a
				1396	href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1397	specifies the formal arguments and return value for the function. The same
				1398	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1399	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1400	in which the function is defined. If this argument is provided, the function
				1401	will automatically be inserted into that module's list of
				1402	functions.</p></li>
				1403
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1404	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1405
				1406	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1407	function is "external", it does not have a body, and thus must be resolved
				1408	by linking with a function defined in a different translation unit.</p></li>
				1409
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1410	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1411	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1412
				1413	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1414	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1415
				1416	<p>These are forwarding methods that make it easy to access the contents of
				1417	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1418	list.</p></li>
				1419
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1420	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1421
				1422	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1423	is necessary to use when you need to update the list or perform a complex
				1424	action that doesn't have a forwarding method.</p></li>
				1425
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1426	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1427	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1428	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1429
				1430	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1431	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1432
				1433	<p>These are forwarding methods that make it easy to access the contents of
				1434	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1435	list.</p></li>
				1436
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1437	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1438
				1439	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1440	necessary to use when you need to update the list or perform a complex
				1441	action that doesn't have a forwarding method.</p></li>
				1442
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1443	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1444
				1445	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1446	function. Because the entry block for the function is always the first
				1447	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1448
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1449	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1450	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1451
				1452	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1453	<tt>Function</tt> and returns the return type of the function, or the <a
				1454	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1455	function.</p></li>
				1456
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1457	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1458
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1459	<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]	1460	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1461	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1462
				1463	</div>
				1464
				1465	<!-- ======================================================================= -->
				1466	<div class="doc_subsection">
				1467	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1468	</div>
				1469
				1470	<div class="doc_text">
				1471
				1472	<p><tt>#include "<a
				1473	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1474	<br>
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1475	doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1476	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1477	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1478
				1479	<p>Global variables are represented with the (suprise suprise)
				1480	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1481	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1482	always referenced by their address (global values must live in memory, so their
				1483	"name" refers to their address). See <a
				1484	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1485	may have an initial value (which must be a <a
				1486	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1487	may be marked as "constant" themselves (indicating that their contents never
				1488	change at runtime).</p>
				1489
				1490	</div>
				1491
				1492	<!-- _______________________________________________________________________ -->
				1493	<div class="doc_subsubsection">
				1494	<a name="m_GlobalVariable">Important Public Members of the
				1495	<tt>GlobalVariable</tt> class</a>
				1496	</div>
				1497
				1498	<div class="doc_text">
				1499
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1500	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1501	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1502	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1503	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1504
				1505	<p>Create a new global variable of the specified type. If
				1506	<tt>isConstant</tt> is true then the global variable will be marked as
				1507	unchanging for the program. The Linkage parameter specifies the type of
				1508	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1509	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1510	the resultant global variable will have internal linkage. AppendingLinkage
				1511	concatenates together all instances (in different translation units) of the
				1512	variable into a single variable but is only applicable to arrays.  See
				1513	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1514	further details on linkage types. Optionally an initializer, a name, and the
				1515	module to put the variable into may be specified for the global variable as
				1516	well.</p></li>
				1517
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1518	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1519
				1520	<p>Returns true if this is a global variable that is known not to
				1521	be modified at runtime.</p></li>
				1522
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1523	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1524
				1525	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1526
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1527	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1528
				1529	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1530	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1531	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1532
				1533	</div>
				1534
				1535	<!-- ======================================================================= -->
				1536	<div class="doc_subsection">
				1537	<a name="Module">The <tt>Module</tt> class</a>
				1538	</div>
				1539
				1540	<div class="doc_text">
				1541
				1542	<p><tt>#include "<a
				1543	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattner	a3da777	2004-06-22 08:02:25 +0000	[diff] [blame]	1544	<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1545
				1546	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1547	programs. An LLVM module is effectively either a translation unit of the
				1548	original program or a combination of several translation units merged by the
				1549	linker. The <tt>Module</tt> class keeps track of a list of <a
				1550	href="#Function"><tt>Function</tt></a>s, a list of <a
				1551	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1552	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1553	helpful member functions that try to make common operations easy.</p>
				1554
				1555	</div>
				1556
				1557	<!-- _______________________________________________________________________ -->
				1558	<div class="doc_subsubsection">
				1559	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1560	</div>
				1561
				1562	<div class="doc_text">
				1563
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1564	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1565	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1566	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1567
				1568	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1569	provide a name for it (probably based on the name of the translation unit).</p>
				1570
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1571	<ul>
				1572	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1573	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1574
				1575	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1576	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1577
				1578	<p>These are forwarding methods that make it easy to access the contents of
				1579	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1580	list.</p></li>
				1581
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1582	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1583
				1584	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1585	necessary to use when you need to update the list or perform a complex
				1586	action that doesn't have a forwarding method.</p>
				1587
				1588	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1589	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1590
				1591	<hr>
				1592
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1593	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1594	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1595
				1596	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1597
				1598	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1599	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1600
				1601	<p> These are forwarding methods that make it easy to access the contents of
				1602	a <tt>Module</tt> object's <a
				1603	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1604
				1605	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1606
				1607	<p>Returns the list of <a
				1608	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1609	use when you need to update the list or perform a complex action that
				1610	doesn't have a forwarding method.</p>
				1611
				1612	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1613	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1614
				1615	<hr>
				1616
				1617	<ul>
				1618	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1619
				1620	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1621	for this <tt>Module</tt>.</p>
				1622
				1623	<p><!-- Convenience methods --></p></li>
				1624	</ul>
				1625
				1626	<hr>
				1627
				1628	<ul>
				1629	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1630	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1631
				1632	<p>Look up the specified function in the <tt>Module</tt> <a
				1633	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1634	<tt>null</tt>.</p></li>
				1635
				1636	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1637	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1638
				1639	<p>Look up the specified function in the <tt>Module</tt> <a
				1640	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1641	external declaration for the function and return it.</p></li>
				1642
				1643	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1644
				1645	<p>If there is at least one entry in the <a
				1646	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1647	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1648	string.</p></li>
				1649
				1650	<li><tt>bool addTypeName(const std::string &Name, const <a
				1651	href="#Type">Type</a> *Ty)</tt>
				1652
				1653	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1654	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1655	name, true is returned and the <a
				1656	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1657	</ul>
				1658
				1659	</div>
				1660
				1661	<!-- ======================================================================= -->
				1662	<div class="doc_subsection">
				1663	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1664	</div>
				1665
				1666	<div class="doc_text">
				1667
				1668	<p>Constant represents a base class for different types of constants. It
				1669	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1670	ConstantArray etc for representing the various types of Constants.</p>
				1671
				1672	</div>
				1673
				1674	<!-- _______________________________________________________________________ -->
				1675	<div class="doc_subsubsection">
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1676	<a name="m_Constant">Important Public Methods</a>
				1677	</div>
				1678	<div class="doc_text">
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1679	</div>
				1680
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1681	<!-- _______________________________________________________________________ -->
				1682	<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1683	<div class="doc_text">
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1684	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1685	<li>ConstantSInt : This subclass of Constant represents a signed integer
				1686	constant.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1687	<ul>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1688	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1689	this constant. </li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1690	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1691	</li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1692	<li>ConstantUInt : This class represents an unsigned integer.
				1693	<ul>
				1694	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value of
				1695	this constant. </li>
				1696	</ul>
				1697	</li>
				1698	<li>ConstantFP : This class represents a floating point constant.
				1699	<ul>
				1700	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1701	this constant. </li>
				1702	</ul>
				1703	</li>
				1704	<li>ConstantBool : This represents a boolean constant.
				1705	<ul>
				1706	<li><tt>bool getValue() const</tt>: Returns the underlying value of this
				1707	constant. </li>
				1708	</ul>
				1709	</li>
				1710	<li>ConstantArray : This represents a constant array.
				1711	<ul>
				1712	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame^]	1713	a vector of component constants that makeup this array. </li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1714	</ul>
				1715	</li>
				1716	<li>ConstantStruct : This represents a constant struct.
				1717	<ul>
				1718	<li><tt>const std::vector<Use> &getValues() const</tt>: Returns
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame^]	1719	a vector of component constants that makeup this array. </li>
Reid Spencer	fe8f4ff	2004-11-01 09:02:53 +0000	[diff] [blame]	1720	</ul>
				1721	</li>
				1722	<li>GlobalValue : This represents either a global variable or a function. In
				1723	either case, the value is a constant fixed address (after linking).
				1724	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1725	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1726	</div>
				1727
				1728	<!-- ======================================================================= -->
				1729	<div class="doc_subsection">
				1730	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1731	</div>
				1732
				1733	<div class="doc_text">
				1734
				1735	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1736	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1737	types are instances of subclasses of type like FunctionType, ArrayType
				1738	etc. DerivedType is the interface for all such dervied types including
				1739	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1740	be recursive (StructType). There exists exactly one instance of any type
				1741	structure at a time. This allows using pointer equality of Type *s for comparing
				1742	types.</p>
				1743
				1744	</div>
				1745
				1746	<!-- _______________________________________________________________________ -->
				1747	<div class="doc_subsubsection">
				1748	<a name="m_Value">Important Public Methods</a>
				1749	</div>
				1750
				1751	<div class="doc_text">
				1752
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1753	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1754
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1755	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1756	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1757	not true for Float and Double. </li>
				1758
				1759	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1760	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1761	return false as they do with isSigned. This returns true for UByteTy,
				1762	UShortTy, UIntTy, and ULongTy. </li>
				1763
Chris Lattner	4573f1b	2004-07-08 17:49:37 +0000	[diff] [blame]	1764	<li><tt>bool isInteger() const</tt>: Equivalent to isSigned() \|\| isUnsigned().</li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1765
				1766	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1767	type, which is either Bool type or one of the Integer types.</li>
				1768
				1769	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1770	floating point types.</li>
				1771
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1772	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1773	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]	1774	example, uint to int or one pointer type to another.</li>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1775	</ul>
				1776	</div>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1777
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1778	<!-- _______________________________________________________________________ -->
				1779	<div class="doc_subsubsection">
				1780	<a name="m_Value">Important Derived Types</a>
				1781	</div>
				1782	<div class="doc_text">
				1783	<ul>
				1784	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1785	<ul>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1786	<li><tt>const Type * getElementType() const</tt>: Returns the type of each
				1787	of the elements in the sequential type. </li>
				1788	</ul>
				1789	</li>
				1790	<li>ArrayType : This is a subclass of SequentialType and defines interface for
				1791	array types.
				1792	<ul>
				1793	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1794	elements in the array. </li>
				1795	</ul>
				1796	</li>
				1797	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1798	<li>StructType : subclass of DerivedTypes for struct types </li>
				1799	<li>FunctionType : subclass of DerivedTypes for function types.
				1800	<ul>
				1801	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1802	function</li>
				1803	<li><tt> const Type * getReturnType() const</tt>: Returns the
				1804	return type of the function.</li>
				1805	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
				1806	the type of the ith parameter.</li>
				1807	<li><tt> const unsigned getNumParams() const</tt>: Returns the
				1808	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1809	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1810	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1811	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1812	</div>
				1813
				1814	<!-- ======================================================================= -->
				1815	<div class="doc_subsection">
				1816	<a name="Argument">The <tt>Argument</tt> class</a>
				1817	</div>
				1818
				1819	<div class="doc_text">
				1820
				1821	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	5836082	2005-01-17 00:12:04 +0000	[diff] [blame^]	1822	arguments to a function. A Function maintains a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1823	arguments. An argument has a pointer to the parent Function.</p>
				1824
				1825	</div>
				1826
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1827	<!-- ======================================================================= -->
				1828	<div class="doc_subsection">
				1829	<a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
				1830	</div>
				1831	<div class="doc_text">
				1832	<p>This class provides a symbol table that the
				1833	<a href="#Function"><tt>Function</tt></a> and <a href="#Module">
				1834	<tt>Module</tt></a> classes use for naming definitions. The symbol table can
				1835	provide a name for any <a href="#Value"><tt>Value</tt></a> or
				1836	<a href="#Type"><tt>Type</tt></a>. <tt>SymbolTable</tt> is an abstract data
				1837	type. It hides the data it contains and provides access to it through a
				1838	controlled interface.</p>
				1839
				1840	<p>To use the <tt>SymbolTable</tt> well, you need to understand the
				1841	structure of the information it holds. The class contains two
				1842	<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
				1843	<tt>Type</tt> to maps of name (<tt>std::string</tt>) to <tt>Value</tt>.
				1844	The second, <tt>tmap</tt>, is a map of names to <tt>Type*</tt>. Thus, Values
				1845	are stored in two-dimensions and accessed by <tt>Type</tt> and name. Types,
				1846	however, are stored in a single dimension and accessed only by name.</p>
				1847
				1848	<p>The interface of this class provides three basic types of operations:
				1849	<ol>
				1850	<li><em>Accessors</em>. Accessors provide read-only access to information
				1851	such as finding a value for a name with the
				1852	<a href="#SymbolTable_lookup">lookup</a> method.</li>
				1853	<li><em>Mutators</em>. Mutators allow the user to add information to the
				1854	<tt>SymbolTable</tt> with methods like
				1855	<a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
				1856	<li><em>Iterators</em>. Iterators allow the user to traverse the content
				1857	of the symbol table in well defined ways, such as the method
				1858	<a href="#SymbolTable_type_begin"><tt>type_begin</tt></a>.</li>
				1859	</ol>
				1860
				1861	<h3>Accessors</h3>
				1862	<dl>
				1863	<dt><tt>Value* lookup(const Type* Ty, const std::string& name) const</tt>:
				1864	</dt>
				1865	<dd>The <tt>lookup</tt> method searches the type plane given by the
				1866	<tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
				1867	If a suitable <tt>Value</tt> is not found, null is returned.</dd>
				1868
				1869	<dt><tt>Type* lookupType( const std::string& name) const</tt>:</dt>
				1870	<dd>The <tt>lookupType</tt> method searches through the types for a
				1871	<tt>Type</tt> with the provided <tt>name</tt>. If a suitable <tt>Type</tt>
				1872	is not found, null is returned.</dd>
				1873
				1874	<dt><tt>bool hasTypes() const</tt>:</dt>
				1875	<dd>This function returns true if an entry has been made into the type
				1876	map.</dd>
				1877
				1878	<dt><tt>bool isEmpty() const</tt>:</dt>
				1879	<dd>This function returns true if both the value and types maps are
				1880	empty</dd>
				1881
				1882	<dt><tt>std::string get_name(const Value*) const</tt>:</dt>
				1883	<dd>This function returns the name of the Value provided or the empty
				1884	string if the Value is not in the symbol table.</dd>
				1885
				1886	<dt><tt>std::string get_name(const Type*) const</tt>:</dt>
				1887	<dd>This function returns the name of the Type provided or the empty
				1888	string if the Type is not in the symbol table.</dd>
				1889	</dl>
				1890
				1891	<h3>Mutators</h3>
				1892	<dl>
				1893	<dt><tt>void insert(Value *Val)</tt>:</dt>
				1894	<dd>This method adds the provided value to the symbol table. The Value must
				1895	have both a name and a type which are extracted and used to place the value
				1896	in the correct type plane under the value's name.</dd>
				1897
				1898	<dt><tt>void insert(const std::string& Name, Value *Val)</tt>:</dt>
				1899	<dd> Inserts a constant or type into the symbol table with the specified
				1900	name. There can be a many to one mapping between names and constants
				1901	or types.</dd>
				1902
				1903	<dt><tt>void insert(const std::string& Name, Type *Typ)</tt>:</dt>
				1904	<dd> Inserts a type into the symbol table with the specified name. There
				1905	can be a many-to-one mapping between names and types. This method
				1906	allows a type with an existing entry in the symbol table to get
				1907	a new name.</dd>
				1908
				1909	<dt><tt>void remove(Value* Val)</tt>:</dt>
				1910	<dd> This method removes a named value from the symbol table. The
				1911	type and name of the Value are extracted from \p N and used to
				1912	lookup the Value in the correct type plane. If the Value is
				1913	not in the symbol table, this method silently ignores the
				1914	request.</dd>
				1915
				1916	<dt><tt>void remove(Type* Typ)</tt>:</dt>
				1917	<dd> This method removes a named type from the symbol table. The
				1918	name of the type is extracted from \P T and used to look up
				1919	the Type in the type map. If the Type is not in the symbol
				1920	table, this method silently ignores the request.</dd>
				1921
				1922	<dt><tt>Value* remove(const std::string& Name, Value *Val)</tt>:</dt>
				1923	<dd> Remove a constant or type with the specified name from the
				1924	symbol table.</dd>
				1925
				1926	<dt><tt>Type* remove(const std::string& Name, Type* T)</tt>:</dt>
				1927	<dd> Remove a type with the specified name from the symbol table.
				1928	Returns the removed Type.</dd>
				1929
				1930	<dt><tt>Value *value_remove(const value_iterator& It)</tt>:</dt>
				1931	<dd> Removes a specific value from the symbol table.
				1932	Returns the removed value.</dd>
				1933
				1934	<dt><tt>bool strip()</tt>:</dt>
				1935	<dd> This method will strip the symbol table of its names leaving
				1936	the type and values. </dd>
				1937
				1938	<dt><tt>void clear()</tt>:</dt>
				1939	<dd>Empty the symbol table completely.</dd>
				1940	</dl>
				1941
				1942	<h3>Iteration</h3>
				1943	<p>The following functions describe three types of iterators you can obtain
				1944	the beginning or end of the sequence for both const and non-const. It is
				1945	important to keep track of the different kinds of iterators. There are
				1946	three idioms worth pointing out:</p>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1947	<table>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1948	<tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
				1949	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1950	<td align="left">Planes Of name/Value maps</td><td>PI</td>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1951	<td align="left"><pre><tt>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1952	for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1953	PE = ST.plane_end(); PI != PE; ++PI ) {
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1954	PI->first // This is the Type* of the plane
				1955	PI->second // This is the SymbolTable::ValueMap of name/Value pairs
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1956	</tt></pre></td>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1957	</tr>
				1958	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1959	<td align="left">All name/Type Pairs</td><td>TI</td>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1960	<td align="left"><pre><tt>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1961	for (SymbolTable::type_const_iterator TI = ST.type_begin(),
				1962	TE = ST.type_end(); TI != TE; ++TI )
				1963	TI->first // This is the name of the type
				1964	TI->second // This is the Type* value associated with the name
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1965	</tt></pre></td>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1966	</tr>
				1967	<tr>
Reid Spencer	d3f876c	2004-11-01 08:19:36 +0000	[diff] [blame]	1968	<td align="left">name/Value pairs in a plane</td><td>VI</td>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1969	<td align="left"><pre><tt>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1970	for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
				1971	VE = ST.value_end(SomeType); VI != VE; ++VI )
				1972	VI->first // This is the name of the Value
				1973	VI->second // This is the Value* value associated with the name
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1974	</tt></pre></td>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1975	</tr>
				1976	</table>
Reid Spencer	c7d1d82	2004-11-01 09:16:30 +0000	[diff] [blame]	1977
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	1978	<p>Using the recommended iterator names and idioms will help you avoid
				1979	making mistakes. Of particular note, make sure that whenever you use
				1980	value_begin(SomeType) that you always compare the resulting iterator
				1981	with value_end(SomeType) not value_end(SomeOtherType) or else you
				1982	will loop infinitely.</p>
				1983
				1984	<dl>
				1985
				1986	<dt><tt>plane_iterator plane_begin()</tt>:</dt>
				1987	<dd>Get an iterator that starts at the beginning of the type planes.
				1988	The iterator will iterate over the Type/ValueMap pairs in the
				1989	type planes. </dd>
				1990
				1991	<dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
				1992	<dd>Get a const_iterator that starts at the beginning of the type
				1993	planes. The iterator will iterate over the Type/ValueMap pairs
				1994	in the type planes. </dd>
				1995
				1996	<dt><tt>plane_iterator plane_end()</tt>:</dt>
				1997	<dd>Get an iterator at the end of the type planes. This serves as
				1998	the marker for end of iteration over the type planes.</dd>
				1999
				2000	<dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
				2001	<dd>Get a const_iterator at the end of the type planes. This serves as
				2002	the marker for end of iteration over the type planes.</dd>
				2003
				2004	<dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
				2005	<dd>Get an iterator that starts at the beginning of a type plane.
				2006	The iterator will iterate over the name/value pairs in the type plane.
				2007	Note: The type plane must already exist before using this.</dd>
				2008
				2009	<dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
				2010	<dd>Get a const_iterator that starts at the beginning of a type plane.
				2011	The iterator will iterate over the name/value pairs in the type plane.
				2012	Note: The type plane must already exist before using this.</dd>
				2013
				2014	<dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
				2015	<dd>Get an iterator to the end of a type plane. This serves as the marker
				2016	for end of iteration of the type plane.
				2017	Note: The type plane must already exist before using this.</dd>
				2018
				2019	<dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
				2020	<dd>Get a const_iterator to the end of a type plane. This serves as the
				2021	marker for end of iteration of the type plane.
				2022	Note: the type plane must already exist before using this.</dd>
				2023
				2024	<dt><tt>type_iterator type_begin()</tt>:</dt>
				2025	<dd>Get an iterator to the start of the name/Type map.</dd>
				2026
				2027	<dt><tt>type_const_iterator type_begin() cons</tt>:</dt>
				2028	<dd> Get a const_iterator to the start of the name/Type map.</dd>
				2029
				2030	<dt><tt>type_iterator type_end()</tt>:</dt>
				2031	<dd>Get an iterator to the end of the name/Type map. This serves as the
				2032	marker for end of iteration of the types.</dd>
				2033
				2034	<dt><tt>type_const_iterator type_end() const</tt>:</dt>
				2035	<dd>Get a const-iterator to the end of the name/Type map. This serves
				2036	as the marker for end of iteration of the types.</dd>
				2037
				2038	<dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
				2039	<dd>This method returns a plane_const_iterator for iteration over
				2040	the type planes starting at a specific plane, given by \p Ty.</dd>
				2041
				2042	<dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
				2043	<dd>This method returns a plane_iterator for iteration over the
				2044	type planes starting at a specific plane, given by \p Ty.</dd>
				2045
				2046	<dt><tt>const ValueMap* findPlane( const Type* Typ ) cons</tt>:</dt>
				2047	<dd>This method returns a ValueMap* for a specific type plane. This
				2048	interface is deprecated and may go away in the future.</dd>
				2049	</dl>
				2050	</div>
				2051
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	2052	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	2053	<hr>
				2054	<address>
				2055	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				2056	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
				2057	<a href="http://validator.w3.org/check/referer"><img
				2058	src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
				2059
				2060	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				2061	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				2062	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				2063	Last modified: $Date$
				2064	</address>
				2065
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	2066	</body>
				2067	</html>
Reid Spencer	096603a	2004-05-26 08:41:35 +0000	[diff] [blame]	2068	<!-- vim: sw=2 noai
				2069	-->