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				4	<head>
				5	<title>LLVM Programmer's Manual</title>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	6	<link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	7	</head>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	8	<body>
				9
				10	<div class="doc_title">
				11	LLVM Programmer's Manual
				12	</div>
				13
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	14	<ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	15	<li><a href="#introduction">Introduction</a></li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	16	<li><a href="#general">General Information</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	17	<ul>
				18	<li><a href="#stl">The C++ Standard Template Library</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	19	<li>The <tt>-time-passes</tt> option
				20	<li>How to use the LLVM Makefile system
				21	<li>How to write a regression test
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	22	--> </li>
Chris Lattner	84b7f8d	2003-08-01 22:20:59 +0000	[diff] [blame]	23	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	24	</li>
				25	<li><a href="#apis">Important and useful LLVM APIs</a>
				26	<ul>
				27	<li><a href="#isa">The <tt>isa<></tt>, <tt>cast<></tt>
				28	and <tt>dyn_cast<></tt> templates</a> </li>
				29	<li><a href="#DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt>
				30	option</a>
				31	<ul>
				32	<li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
				33	and the <tt>-debug-only</tt> option</a> </li>
				34	</ul>
				35	</li>
				36	<li><a href="#Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				37	option</a><!--
Chris Lattner	986e0c9	2002-09-22 19:38:40 +0000	[diff] [blame]	38	<li>The <tt>InstVisitor</tt> template
				39	<li>The general graph API
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	40	--> </li>
				41	</ul>
				42	</li>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	43	<li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	44	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	45	<li><a href="#inspection">Basic Inspection and Traversal Routines</a>
				46	<ul>
				47	<li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
				48	in a <tt>Function</tt></a> </li>
				49	<li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
				50	in a <tt>BasicBlock</tt></a> </li>
				51	<li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
				52	in a <tt>Function</tt></a> </li>
				53	<li><a href="#iterate_convert">Turning an iterator into a
				54	class pointer</a> </li>
				55	<li><a href="#iterate_complex">Finding call sites: a more
				56	complex example</a> </li>
				57	<li><a href="#calls_and_invokes">Treating calls and invokes
				58	the same way</a> </li>
				59	<li><a href="#iterate_chains">Iterating over def-use &
				60	use-def chains</a> </li>
				61	</ul>
				62	</li>
				63	<li><a href="#simplechanges">Making simple changes</a>
				64	<ul>
				65	<li><a href="#schanges_creating">Creating and inserting new
				66	<tt>Instruction</tt>s</a> </li>
				67	<li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
				68	<li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
				69	with another <tt>Value</tt></a> </li>
				70	</ul>
Chris Lattner	ae7f759	2002-09-06 18:31:18 +0000	[diff] [blame]	71	<!--
				72	<li>Working with the Control Flow Graph
				73	<ul>
				74	<li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
				75	<li>
				76	<li>
				77	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	78	--> </li>
				79	</ul>
				80	</li>
Joel Stanley	9b96c44	2002-09-06 21:55:13 +0000	[diff] [blame]	81	<li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	82	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	83	<li><a href="#Value">The <tt>Value</tt> class</a>
				84	<ul>
				85	<li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	86	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	87	<li><a href="#Instruction">The <tt>Instruction</tt> class</a>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	88	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	89	<li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt>
				90	class</a></li>
				91	</ul></li>
				92	<li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
				93	<ul>
				94	<li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
				95	<li><a href="#Function">The <tt>Function</tt> class</a></li>
				96	<li><a href="#GlobalVariable">The <tt>GlobalVariable</tt>
				97	class</a></li>
				98	</ul></li>
				99	<li><a href="#Module">The <tt>Module</tt> class</a></li>
				100	<li><a href="#Constant">The <tt>Constant</tt> class</a>
				101	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	102	<li> <br>
				103	</li>
				104	<li> <br>
				105	</li>
				106	</ul>
				107	</li>
				108	</ul>
				109	</li>
				110	<li><a href="#Type">The <tt>Type</tt> class</a> </li>
				111	<li><a href="#Argument">The <tt>Argument</tt> class</a> </li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	112	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	113	</li>
				114	<li>The <tt>SymbolTable</tt> class </li>
				115	<li>The <tt>ilist</tt> and <tt>iplist</tt> classes
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	116	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	117	<li>Creating, inserting, moving and deleting from LLVM lists </li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	118	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	119	</li>
				120	<li>Important iterator invalidation semantics to be aware of </li>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	121	</ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	122	</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
				125	<div class="doc_text">
				126	<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
				127	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>, and <a
				128	href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a></b></p>
				129	</div>
				130
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	131	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	132	<div class="doc_section">
				133	<a name="introduction">Introduction </a>
				134	</div>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	135	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	136
				137	<div class="doc_text">
				138
				139	<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]	140	interfaces available in the LLVM source-base. This manual is not
				141	intended to explain what LLVM is, how it works, and what LLVM code looks
				142	like. It assumes that you know the basics of LLVM and are interested
				143	in writing transformations or otherwise analyzing or manipulating the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	144	code.</p>
				145
				146	<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]	147	way in the continuously growing source code that makes up the LLVM
				148	infrastructure. Note that this manual is not intended to serve as a
				149	replacement for reading the source code, so if you think there should be
				150	a method in one of these classes to do something, but it's not listed,
				151	check the source. Links to the <a href="/doxygen/">doxygen</a> sources
				152	are provided to make this as easy as possible.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	153
				154	<p>The first section of this document describes general information that is
				155	useful to know when working in the LLVM infrastructure, and the second describes
				156	the Core LLVM classes. In the future this manual will be extended with
				157	information describing how to use extension libraries, such as dominator
				158	information, CFG traversal routines, and useful utilities like the <tt><a
				159	href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
				160
				161	</div>
				162
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	163	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	164	<div class="doc_section">
				165	<a name="general">General Information</a>
				166	</div>
				167	<!-- *********************************************************************** -->
				168
				169	<div class="doc_text">
				170
				171	<p>This section contains general information that is useful if you are working
				172	in the LLVM source-base, but that isn't specific to any particular API.</p>
				173
				174	</div>
				175
				176	<!-- ======================================================================= -->
				177	<div class="doc_subsection">
				178	<a name="stl">The C++ Standard Template Library</a>
				179	</div>
				180
				181	<div class="doc_text">
				182
				183	<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	184	perhaps much more than you are used to, or have seen before. Because of
				185	this, you might want to do a little background reading in the
				186	techniques used and capabilities of the library. There are many good
				187	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]	188	can get, so it will not be discussed in this document.</p>
				189
				190	<p>Here are some useful links:</p>
				191
				192	<ol>
				193
				194	<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
				195	reference</a> - an excellent reference for the STL and other parts of the
				196	standard C++ library.</li>
				197
				198	<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
				199	O'Reilly book in the making. It has a decent <a
				200	href="http://www.tempest-sw.com/cpp/ch13-libref.html">Standard Library
				201	Reference</a> that rivals Dinkumware's, and is actually free until the book is
				202	published.</li>
				203
				204	<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
				205	Questions</a></li>
				206
				207	<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
				208	Contains a useful <a
				209	href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
				210	STL</a>.</li>
				211
				212	<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
				213	Page</a></li>
				214
				215	</ol>
				216
				217	<p>You are also encouraged to take a look at the <a
				218	href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
				219	to write maintainable code more than where to put your curly braces.</p>
				220
				221	</div>
				222
				223	<!-- ======================================================================= -->
				224	<div class="doc_subsection">
				225	<a name="stl">Other useful references</a>
				226	</div>
				227
				228	<div class="doc_text">
				229
				230	<p>LLVM is currently using CVS as its source versioning system. You may find
				231	this reference handy:</p>
				232
				233	<ol>
				234	<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	235	Branch and Tag Primer</a></li>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	236	</ol>
				237
				238	</div>
				239
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	240	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	241	<div class="doc_section">
				242	<a name="apis">Important and useful LLVM APIs</a>
				243	</div>
				244	<!-- *********************************************************************** -->
				245
				246	<div class="doc_text">
				247
				248	<p>Here we highlight some LLVM APIs that are generally useful and good to
				249	know about when writing transformations.</p>
				250
				251	</div>
				252
				253	<!-- ======================================================================= -->
				254	<div class="doc_subsection">
				255	<a name="isa">The isa<>, cast<> and dyn_cast<> templates</a>
				256	</div>
				257
				258	<div class="doc_text">
				259
				260	<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]	261	These templates have many similarities to the C++ <tt>dynamic_cast<></tt>
				262	operator, but they don't have some drawbacks (primarily stemming from
				263	the fact that <tt>dynamic_cast<></tt> only works on classes that
				264	have a v-table). Because they are used so often, you must know what they
				265	do and how they work. All of these templates are defined in the <a
				266	href="/doxygen/Casting_8h-source.html"><tt>Support/Casting.h</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	267	file (note that you very rarely have to include this file directly).</p>
				268
				269	<dl>
				270	<dt><tt>isa<></tt>: </dt>
				271
				272	<dd>The <tt>isa<></tt> operator works exactly like the Java
				273	"<tt>instanceof</tt>" operator. It returns true or false depending on whether
				274	a reference or pointer points to an instance of the specified class. This can
				275	be very useful for constraint checking of various sorts (example below).</dd>
				276
				277	<dt><tt>cast<></tt>: </dt>
				278
				279	<dd>The <tt>cast<></tt> operator is a "checked cast" operation. It
				280	converts a pointer or reference from a base class to a derived cast, causing
				281	an assertion failure if it is not really an instance of the right type. This
				282	should be used in cases where you have some information that makes you believe
				283	that something is of the right type. An example of the <tt>isa<></tt>
				284	and <tt>cast<></tt> template is:
				285
				286	<pre>static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const
				287	Loop *L) {<br> if (isa<<a href="#Constant">Constant</a>>(V) \|\| isa<<a
				288	href="#Argument">Argument</a>>(V) \|\| isa<<a
				289	href="#GlobalValue">GlobalValue</a>>(V))<br> return true;<br><br> <i>//
				290	Otherwise, it must be an instruction...</i><br> return
				291	!L->contains(cast<<a
				292	href="#Instruction">Instruction</a>>(V)->getParent());<br></pre>
				293
				294	<p>Note that you should <b>not</b> use an <tt>isa<></tt> test followed
				295	by a <tt>cast<></tt>, for that use the <tt>dyn_cast<></tt>
				296	operator.</p>
				297
				298	</dd>
				299
				300	<dt><tt>dyn_cast<></tt>:</dt>
				301
				302	<dd>The <tt>dyn_cast<></tt> operator is a "checking cast" operation. It
				303	checks to see if the operand is of the specified type, and if so, returns a
				304	pointer to it (this operator does not work with references). If the operand is
				305	not of the correct type, a null pointer is returned. Thus, this works very
				306	much like the <tt>dynamic_cast</tt> operator in C++, and should be used in the
				307	same circumstances. Typically, the <tt>dyn_cast<></tt> operator is used
				308	in an <tt>if</tt> statement or some other flow control statement like this:
				309
				310	<pre> if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast<<a
				311	href="#AllocationInst">AllocationInst</a>>(Val)) {<br> ...<br> }<br></pre>
				312
				313	<p> This form of the <tt>if</tt> statement effectively combines together a
				314	call to <tt>isa<></tt> and a call to <tt>cast<></tt> into one
				315	statement, which is very convenient.</p>
				316
				317	<p> Another common example is:</p>
				318
				319	<pre> <i>// Loop over all of the phi nodes in a basic block</i><br>
				320	BasicBlock::iterator BBI = BB->begin();<br> for (; <a
				321	href="#PhiNode">PHINode</a> *PN = dyn_cast<<a
				322	href="#PHINode">PHINode</a>>(BBI); ++BBI)<br> cerr << *PN;<br></pre>
				323
				324	<p>Note that the <tt>dyn_cast<></tt> operator, like C++'s
				325	<tt>dynamic_cast</tt> or Java's <tt>instanceof</tt> operator, can be abused.
				326	In particular you should not use big chained <tt>if/then/else</tt> blocks to
				327	check for lots of different variants of classes. If you find yourself
				328	wanting to do this, it is much cleaner and more efficient to use the
				329	InstVisitor class to dispatch over the instruction type directly.</p>
				330
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	331	</dd>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	332
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	333	<dt><tt>cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	334
				335	<dd>The <tt>cast_or_null<></tt> operator works just like the
				336	<tt>cast<></tt> operator, except that it allows for a null pointer as
				337	an argument (which it then propagates). This can sometimes be useful,
				338	allowing you to combine several null checks into one.</dd>
				339
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	340	<dt><tt>dyn_cast_or_null<></tt>: </dt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	341
				342	<dd>The <tt>dyn_cast_or_null<></tt> operator works just like the
				343	<tt>dyn_cast<></tt> operator, except that it allows for a null pointer
				344	as an argument (which it then propagates). This can sometimes be useful,
				345	allowing you to combine several null checks into one.</dd>
				346
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	347	</dl>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	348
				349	<p>These five templates can be used with any classes, whether they have a
				350	v-table or not. To add support for these templates, you simply need to add
				351	<tt>classof</tt> static methods to the class you are interested casting
				352	to. Describing this is currently outside the scope of this document, but there
				353	are lots of examples in the LLVM source base.</p>
				354
				355	</div>
				356
				357	<!-- ======================================================================= -->
				358	<div class="doc_subsection">
				359	<a name="DEBUG">The <tt>DEBUG()</tt> macro & <tt>-debug</tt> option</a>
				360	</div>
				361
				362	<div class="doc_text">
				363
				364	<p>Often when working on your pass you will put a bunch of debugging printouts
				365	and other code into your pass. After you get it working, you want to remove
				366	it... but you may need it again in the future (to work out new bugs that you run
				367	across).</p>
				368
				369	<p> Naturally, because of this, you don't want to delete the debug printouts,
				370	but you don't want them to always be noisy. A standard compromise is to comment
				371	them out, allowing you to enable them if you need them in the future.</p>
				372
				373	<p>The "<tt><a href="/doxygen/Debug_8h-source.html">Support/Debug.h</a></tt>"
				374	file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
				375	this problem. Basically, you can put arbitrary code into the argument of the
				376	<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
				377	tool) is run with the '<tt>-debug</tt>' command line argument:</p>
				378
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	379	<pre> ... <br> DEBUG(std::cerr << "I am here!\n");<br> ...<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	380
				381	<p>Then you can run your pass like this:</p>
				382
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	383	<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]	384
				385	<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
				386	to not have to create "yet another" command line option for the debug output for
				387	your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
				388	so they do not cause a performance impact at all (for the same reason, they
				389	should also not contain side-effects!).</p>
				390
				391	<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
				392	enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
				393	"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
				394	program hasn't been started yet, you can always just run it with
				395	<tt>-debug</tt>.</p>
				396
				397	</div>
				398
				399	<!-- _______________________________________________________________________ -->
				400	<div class="doc_subsubsection">
				401	<a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE()</tt> and
				402	the <tt>-debug-only</tt> option</a>
				403	</div>
				404
				405	<div class="doc_text">
				406
				407	<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
				408	just turns on <b>too much</b> information (such as when working on the code
				409	generator). If you want to enable debug information with more fine-grained
				410	control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
				411	option as follows:</p>
				412
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	413	<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]	414
				415	<p>Then you can run your pass like this:</p>
				416
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	417	<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]	418
				419	<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
				420	a file, to specify the debug type for the entire module (if you do this before
				421	you <tt>#include "Support/Debug.h"</tt>, you don't have to insert the ugly
				422	<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
				423	"bar", because there is no system in place to ensure that names do not
				424	conflict. If two different modules use the same string, they will all be turned
				425	on when the name is specified. This allows, for example, all debug information
				426	for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	427	even if the source lives in multiple files.</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	428
				429	</div>
				430
				431	<!-- ======================================================================= -->
				432	<div class="doc_subsection">
				433	<a name="Statistic">The <tt>Statistic</tt> template & <tt>-stats</tt>
				434	option</a>
				435	</div>
				436
				437	<div class="doc_text">
				438
				439	<p>The "<tt><a
				440	href="/doxygen/Statistic_8h-source.html">Support/Statistic.h</a></tt>" file
				441	provides a template named <tt>Statistic</tt> that is used as a unified way to
				442	keep track of what the LLVM compiler is doing and how effective various
				443	optimizations are. It is useful to see what optimizations are contributing to
				444	making a particular program run faster.</p>
				445
				446	<p>Often you may run your pass on some big program, and you're interested to see
				447	how many times it makes a certain transformation. Although you can do this with
				448	hand inspection, or some ad-hoc method, this is a real pain and not very useful
				449	for big programs. Using the <tt>Statistic</tt> template makes it very easy to
				450	keep track of this information, and the calculated information is presented in a
				451	uniform manner with the rest of the passes being executed.</p>
				452
				453	<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
				454	it are as follows:</p>
				455
				456	<ol>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	457	<li>Define your statistic like this:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	458	<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]	459
				460	<p>The <tt>Statistic</tt> template can emulate just about any data-type,
				461	but if you do not specify a template argument, it defaults to acting like
				462	an unsigned int counter (this is usually what you want).</p></li>
				463
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	464	<li>Whenever you make a transformation, bump the counter:
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	465	<pre> ++NumXForms; // I did stuff<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	466	</li>
				467	</ol>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	468
				469	<p>That's all you have to do. To get '<tt>opt</tt>' to print out the
				470	statistics gathered, use the '<tt>-stats</tt>' option:</p>
				471
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	472	<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]	473
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	474	<p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
				475	suite, it gives a report that looks like this:</p>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	476
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	477	<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]	478
				479	<p>Obviously, with so many optimizations, having a unified framework for this
				480	stuff is very nice. Making your pass fit well into the framework makes it more
				481	maintainable and useful.</p>
				482
				483	</div>
				484
				485	<!-- *********************************************************************** -->
				486	<div class="doc_section">
				487	<a name="common">Helpful Hints for Common Operations</a>
				488	</div>
				489	<!-- *********************************************************************** -->
				490
				491	<div class="doc_text">
				492
				493	<p>This section describes how to perform some very simple transformations of
				494	LLVM code. This is meant to give examples of common idioms used, showing the
				495	practical side of LLVM transformations. <p> Because this is a "how-to" section,
				496	you should also read about the main classes that you will be working with. The
				497	<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
				498	and descriptions of the main classes that you should know about.</p>
				499
				500	</div>
				501
				502	<!-- NOTE: this section should be heavy on example code -->
				503	<!-- ======================================================================= -->
				504	<div class="doc_subsection">
				505	<a name="inspection">Basic Inspection and Traversal Routines</a>
				506	</div>
				507
				508	<div class="doc_text">
				509
				510	<p>The LLVM compiler infrastructure have many different data structures that may
				511	be traversed. Following the example of the C++ standard template library, the
				512	techniques used to traverse these various data structures are all basically the
				513	same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
				514	method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
				515	function returns an iterator pointing to one past the last valid element of the
				516	sequence, and there is some <tt>XXXiterator</tt> data type that is common
				517	between the two operations.</p>
				518
				519	<p>Because the pattern for iteration is common across many different aspects of
				520	the program representation, the standard template library algorithms may be used
				521	on them, and it is easier to remember how to iterate. First we show a few common
				522	examples of the data structures that need to be traversed. Other data
				523	structures are traversed in very similar ways.</p>
				524
				525	</div>
				526
				527	<!-- _______________________________________________________________________ -->
				528	<div class="subsubsection">
				529	<a name="iterate_function">Iterating over the </a><a
				530	href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
				531	href="#Function"><tt>Function</tt></a>
				532	</div>
				533
				534	<div class="doc_text">
				535
				536	<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
				537	transform in some way; in particular, you'd like to manipulate its
				538	<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
				539	the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
				540	an example that prints the name of a <tt>BasicBlock</tt> and the number of
				541	<tt>Instruction</tt>s it contains:</p>
				542
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	543	<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]	544
				545	<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]	546	invoking member functions of the <tt>Instruction</tt> class. This is
				547	because the indirection operator is overloaded for the iterator
Chris Lattner	7496ec5	2003-08-05 22:54:23 +0000	[diff] [blame]	548	classes. In the above code, the expression <tt>i->size()</tt> is
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	549	exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
				550
				551	</div>
				552
				553	<!-- _______________________________________________________________________ -->
				554	<div class="subsubsection">
				555	<a name="iterate_basicblock">Iterating over the </a><a
				556	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				557	href="#BasicBlock"><tt>BasicBlock</tt></a>
				558	</div>
				559
				560	<div class="doc_text">
				561
				562	<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
				563	easy to iterate over the individual instructions that make up
				564	<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
				565	a <tt>BasicBlock</tt>:</p>
				566
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	567	<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]	568
				569	<p>However, this isn't really the best way to print out the contents of a
				570	<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
				571	anything you'll care about, you could have just invoked the print routine on the
				572	basic block itself: <tt>cerr << *blk << "\n";</tt>.</p>
				573
				574	<p>Note that currently operator<< is implemented for <tt>Value*</tt>, so
				575	it will print out the contents of the pointer, instead of the pointer value you
				576	might expect. This is a deprecated interface that will be removed in the
				577	future, so it's best not to depend on it. To print out the pointer value for
				578	now, you must cast to <tt>void*</tt>.</p>
				579
				580	</div>
				581
				582	<!-- _______________________________________________________________________ -->
				583	<div class="subsubsection">
				584	<a name="iterate_institer">Iterating over the </a><a
				585	href="#Instruction"><tt>Instruction</tt></a>s in a <a
				586	href="#Function"><tt>Function</tt></a>
				587	</div>
				588
				589	<div class="doc_text">
				590
				591	<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
				592	<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
				593	<tt>InstIterator</tt> should be used instead. You'll need to include <a
				594	href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
				595	and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
				596	small example that shows how to dump all instructions in a function to stderr
				597	(<b>Note:</b> Dereferencing an <tt>InstIterator</tt> yields an
				598	<tt>Instruction*</tt>, <i>not</i> an <tt>Instruction&</tt>!):</p>
				599
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	600	<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]	601	Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
				602	worklist with its initial contents. For example, if you wanted to
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	603	initialize a worklist to contain all instructions in a <tt>Function</tt>
				604	F, all you would need to do is something like:
				605	<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]	606
				607	<p>The STL set <tt>worklist</tt> would now contain all instructions in the
				608	<tt>Function</tt> pointed to by F.</p>
				609
				610	</div>
				611
				612	<!-- _______________________________________________________________________ -->
				613	<div class="doc_subsubsection">
				614	<a name="iterate_convert">Turning an iterator into a class pointer (and
				615	vice-versa)</a>
				616	</div>
				617
				618	<div class="doc_text">
				619
				620	<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]	621	instance when all you've got at hand is an iterator. Well, extracting
				622	a reference or a pointer from an iterator is very straightforward.
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	623	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]	624	is a <tt>BasicBlock::const_iterator</tt>:</p>
				625
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	626	<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]	627
				628	<p>However, the iterators you'll be working with in the LLVM framework are
				629	special: they will automatically convert to a ptr-to-instance type whenever they
				630	need to. Instead of dereferencing the iterator and then taking the address of
				631	the result, you can simply assign the iterator to the proper pointer type and
				632	you get the dereference and address-of operation as a result of the assignment
				633	(behind the scenes, this is a result of overloading casting mechanisms). Thus
				634	the last line of the last example,</p>
				635
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	636	<pre>Instruction* pinst = &*i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	637
				638	<p>is semantically equivalent to</p>
				639
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	640	<pre>Instruction* pinst = i;</pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	641
				642	<p>It's also possible to turn a class pointer into the corresponding iterator.
				643	Usually, this conversion is quite inexpensive. The following code snippet
				644	illustrates use of the conversion constructors provided by LLVM iterators. By
				645	using these, you can explicitly grab the iterator of something without actually
				646	obtaining it via iteration over some structure:</p>
				647
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	648	<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]	649
				650	<p>Of course, this example is strictly pedagogical, because it'd be much
				651	better to explicitly grab the next instruction directly from inst.</p>
				652
				653	</div>
				654
				655	<!--_______________________________________________________________________-->
				656	<div class="doc_subsubsection">
				657	<a name="iterate_complex">Finding call sites: a slightly more complex
				658	example</a>
				659	</div>
				660
				661	<div class="doc_text">
				662
				663	<p>Say that you're writing a FunctionPass and would like to count all the
				664	locations in the entire module (that is, across every <tt>Function</tt>) where a
				665	certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
				666	learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
				667	much more straightforward manner, but this example will allow us to explore how
				668	you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
				669	is what we want to do:</p>
				670
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	671	<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]	672
				673	<p>And the actual code is (remember, since we're writing a
				674	<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
				675	override the <tt>runOnFunction</tt> method...):</p>
				676
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	677	<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
				678	href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a><<a
				679	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]	680
				681	</div>
				682
Brian Gaeke	f1972c6	2003-11-07 19:25:45 +0000	[diff] [blame]	683	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	684	<div class="doc_subsubsection">
				685	<a name="calls_and_invokes">Treating calls and invokes the same way</a>
				686	</div>
				687
				688	<div class="doc_text">
				689
				690	<p>You may have noticed that the previous example was a bit oversimplified in
				691	that it did not deal with call sites generated by 'invoke' instructions. In
				692	this, and in other situations, you may find that you want to treat
				693	<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
				694	most-specific common base class is <tt>Instruction</tt>, which includes lots of
				695	less closely-related things. For these cases, LLVM provides a handy wrapper
				696	class called <a
				697	href="http://llvm.cs.uiuc.edu/doxygen/classCallSite.html"><tt>CallSite
				698	</tt></a>. It is essentially a wrapper around an <tt>Instruction</tt> pointer,
				699	with some methods that provide functionality common to <tt>CallInst</tt>s and
				700	<tt>InvokeInst</tt>s.</p>
				701
				702	<p>This class is supposed to have "value semantics". So it should be passed by
				703	value, not by reference; it should not be dynamically allocated or deallocated
				704	using <tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently
				705	copyable, assignable and constructable, with costs equivalents to that of a bare
				706	pointer. (You will notice, if you look at its definition, that it has only a
				707	single data member.)</p>
				708
				709	</div>
				710
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	711	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	712	<div class="doc_subsubsection">
				713	<a name="iterate_chains">Iterating over def-use & use-def chains</a>
				714	</div>
				715
				716	<div class="doc_text">
				717
				718	<p>Frequently, we might have an instance of the <a
				719	href="/doxygen/classValue.html">Value Class</a> and we want to determine which
				720	<tt>User</tt>s use the <tt>Value</tt>. The list of all <tt>User</tt>s of a
				721	particular <tt>Value</tt> is called a <i>def-use</i> chain. For example, let's
				722	say we have a <tt>Function*</tt> named <tt>F</tt> to a particular function
				723	<tt>foo</tt>. Finding all of the instructions that <i>use</i> <tt>foo</tt> is as
				724	simple as iterating over the <i>def-use</i> chain of <tt>F</tt>:</p>
				725
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	726	<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]	727
				728	<p>Alternately, it's common to have an instance of the <a
				729	href="/doxygen/classUser.html">User Class</a> and need to know what
				730	<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
				731	<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
				732	<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
				733	all of the values that a particular instruction uses (that is, the operands of
				734	the particular <tt>Instruction</tt>):</p>
				735
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	736	<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]	737
Chris Lattner	1a3105b	2002-09-09 05:49:39 +0000	[diff] [blame]	738	<!--
				739	def-use chains ("finding all users of"): Value::use_begin/use_end
				740	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]	741	-->
				742
				743	</div>
				744
				745	<!-- ======================================================================= -->
				746	<div class="doc_subsection">
				747	<a name="simplechanges">Making simple changes</a>
				748	</div>
				749
				750	<div class="doc_text">
				751
				752	<p>There are some primitive transformation operations present in the LLVM
Joel Stanley	753eb71	2002-09-11 22:32:24 +0000	[diff] [blame]	753	infrastructure that are worth knowing about. When performing
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	754	transformations, it's fairly common to manipulate the contents of basic
				755	blocks. This section describes some of the common methods for doing so
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	756	and gives example code.</p>
				757
				758	</div>
				759
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	760	<!--_______________________________________________________________________-->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	761	<div class="doc_subsubsection">
				762	<a name="schanges_creating">Creating and inserting new
				763	<tt>Instruction</tt>s</a>
				764	</div>
				765
				766	<div class="doc_text">
				767
				768	<p><i>Instantiating Instructions</i></p>
				769
				770	<p>Creation of <tt>Instruction</tt>s is straightforward: simply call the
				771	constructor for the kind of instruction to instantiate and provide the necessary
				772	parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
				773	(const-ptr-to) <tt>Type</tt>. Thus:</p>
				774
				775	<pre>AllocaInst* ai = new AllocaInst(Type::IntTy);</pre>
				776
				777	<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
				778	one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
				779	subclass is likely to have varying default parameters which change the semantics
				780	of the instruction, so refer to the <a
				781	href="/doxygen/classInstruction.html">doxygen documentation for the subclass of
				782	Instruction</a> that you're interested in instantiating.</p>
				783
				784	<p><i>Naming values</i></p>
				785
				786	<p>It is very useful to name the values of instructions when you're able to, as
				787	this facilitates the debugging of your transformations. If you end up looking
				788	at generated LLVM machine code, you definitely want to have logical names
				789	associated with the results of instructions! By supplying a value for the
				790	<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
				791	associate a logical name with the result of the instruction's execution at
				792	runtime. For example, say that I'm writing a transformation that dynamically
				793	allocates space for an integer on the stack, and that integer is going to be
				794	used as some kind of index by some other code. To accomplish this, I place an
				795	<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
				796	<tt>Function</tt>, and I'm intending to use it within the same
				797	<tt>Function</tt>. I might do:</p>
				798
				799	<pre>AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");</pre>
				800
				801	<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
				802	execution value, which is a pointer to an integer on the runtime stack.</p>
				803
				804	<p><i>Inserting instructions</i></p>
				805
				806	<p>There are essentially two ways to insert an <tt>Instruction</tt>
				807	into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
				808
Joel Stanley	9dd1ad6	2002-09-18 03:17:23 +0000	[diff] [blame]	809	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	810	<li>Insertion into an explicit instruction list
				811
				812	<p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
				813	<tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
				814	before <tt>*pi</tt>, we do the following: </p>
				815
				816	<pre> BasicBlock pb = ...;<br> Instruction pi = ...;<br> Instruction *newInst = new Instruction(...);<br> pb->getInstList().insert(pi, newInst); // inserts newInst before pi in pb<br></pre></li>
				817
				818	<li>Insertion into an implicit instruction list
				819
				820	<p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
				821	are implicitly associated with an existing instruction list: the instruction
				822	list of the enclosing basic block. Thus, we could have accomplished the same
				823	thing as the above code without being given a <tt>BasicBlock</tt> by doing:
				824	</p>
				825
				826	<pre> Instruction pi = ...;<br> Instruction newInst = new Instruction(...);<br> pi->getParent()->getInstList().insert(pi, newInst);<br></pre>
				827
				828	<p>In fact, this sequence of steps occurs so frequently that the
				829	<tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
				830	constructors which take (as a default parameter) a pointer to an
				831	<tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
				832	precede. That is, <tt>Instruction</tt> constructors are capable of
				833	inserting the newly-created instance into the <tt>BasicBlock</tt> of a
				834	provided instruction, immediately before that instruction. Using an
				835	<tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
				836	parameter, the above code becomes:</p>
				837
				838	<pre>Instruction* pi = ...;<br>Instruction* newInst = new Instruction(..., pi);<br></pre>
				839
				840	<p>which is much cleaner, especially if you're creating a lot of
				841	instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
				842	</ul>
				843
				844	</div>
				845
				846	<!--_______________________________________________________________________-->
				847	<div class="doc_subsubsection">
				848	<a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
				849	</div>
				850
				851	<div class="doc_text">
				852
				853	<p>Deleting an instruction from an existing sequence of instructions that form a
				854	<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straightforward. First,
				855	you must have a pointer to the instruction that you wish to delete. Second, you
				856	need to obtain the pointer to that instruction's basic block. You use the
				857	pointer to the basic block to get its list of instructions and then use the
				858	erase function to remove your instruction. For example:</p>
				859
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	860	<pre> <a href="#Instruction">Instruction</a> *I = .. ;<br> <a
				861	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]	862
				863	</div>
				864
				865	<!--_______________________________________________________________________-->
				866	<div class="doc_subsubsection">
				867	<a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
				868	<tt>Value</tt></a>
				869	</div>
				870
				871	<div class="doc_text">
				872
				873	<p><i>Replacing individual instructions</i></p>
				874
				875	<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]	876	permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	877	and <tt>ReplaceInstWithInst</tt>.</p>
				878
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	879	<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	880
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	881	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	882	<li><tt>ReplaceInstWithValue</tt>
				883
				884	<p>This function replaces all uses (within a basic block) of a given
				885	instruction with a value, and then removes the original instruction. The
				886	following example illustrates the replacement of the result of a particular
				887	<tt>AllocaInst</tt> that allocates memory for a single integer with an null
				888	pointer to an integer.</p>
				889
				890	<pre>AllocaInst* instToReplace = ...;<br>BasicBlock::iterator ii(instToReplace);<br>ReplaceInstWithValue(instToReplace->getParent()->getInstList(), ii,<br> Constant::getNullValue(PointerType::get(Type::IntTy)));<br></pre></li>
				891
				892	<li><tt>ReplaceInstWithInst</tt>
				893
				894	<p>This function replaces a particular instruction with another
				895	instruction. The following example illustrates the replacement of one
				896	<tt>AllocaInst</tt> with another.</p>
				897
				898	<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]	899	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	900
				901	<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
				902
				903	<p>You can use <tt>Value::replaceAllUsesWith</tt> and
				904	<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
				905	doxygen documentation for the <a href="/doxygen/classValue.html">Value Class</a>
				906	and <a href="/doxygen/classUser.html">User Class</a>, respectively, for more
				907	information.</p>
				908
				909	<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
				910	include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
				911	ReplaceInstWithValue, ReplaceInstWithInst -->
				912
				913	</div>
				914
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	915	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	916	<div class="doc_section">
				917	<a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
				918	</div>
				919	<!-- *********************************************************************** -->
				920
				921	<div class="doc_text">
				922
				923	<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]	924	being inspected or transformed. The core LLVM classes are defined in
				925	header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	926	the <tt>lib/VMCore</tt> directory.</p>
				927
				928	</div>
				929
				930	<!-- ======================================================================= -->
				931	<div class="doc_subsection">
				932	<a name="Value">The <tt>Value</tt> class</a>
				933	</div>
				934
				935	<div>
				936
				937	<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
				938	<br>
				939	doxygen info: <a href="/doxygen/classValue.html">Value Class</a></p>
				940
				941	<p>The <tt>Value</tt> class is the most important class in the LLVM Source
				942	base. It represents a typed value that may be used (among other things) as an
				943	operand to an instruction. There are many different types of <tt>Value</tt>s,
				944	such as <a href="#Constant"><tt>Constant</tt></a>s,<a
				945	href="#Argument"><tt>Argument</tt></a>s. Even <a
				946	href="#Instruction"><tt>Instruction</tt></a>s and <a
				947	href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
				948
				949	<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
				950	for a program. For example, an incoming argument to a function (represented
				951	with an instance of the <a href="#Argument">Argument</a> class) is "used" by
				952	every instruction in the function that references the argument. To keep track
				953	of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
				954	href="#User"><tt>User</tt></a>s that is using it (the <a
				955	href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
				956	graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
				957	def-use information in the program, and is accessible through the <tt>use_</tt>*
				958	methods, shown below.</p>
				959
				960	<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
				961	and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
				962	method. In addition, all LLVM values can be named. The "name" of the
				963	<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
				964
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	965	<pre> %<b>foo</b> = add int 1, 2<br></pre>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	966
				967	<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
				968	that the name of any value may be missing (an empty string), so names should
				969	<b>ONLY</b> be used for debugging (making the source code easier to read,
				970	debugging printouts), they should not be used to keep track of values or map
				971	between them. For this purpose, use a <tt>std::map</tt> of pointers to the
				972	<tt>Value</tt> itself instead.</p>
				973
				974	<p>One important aspect of LLVM is that there is no distinction between an SSA
				975	variable and the operation that produces it. Because of this, any reference to
				976	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]	977	argument, for example) is represented as a direct pointer to the instance of
				978	the class that
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	979	represents this value. Although this may take some getting used to, it
				980	simplifies the representation and makes it easier to manipulate.</p>
				981
				982	</div>
				983
				984	<!-- _______________________________________________________________________ -->
				985	<div class="doc_subsubsection">
				986	<a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
				987	</div>
				988
				989	<div class="doc_text">
				990
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	991	<ul>
				992	<li><tt>Value::use_iterator</tt> - Typedef for iterator over the
				993	use-list<br>
				994	<tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
				995	the use-list<br>
				996	<tt>unsigned use_size()</tt> - Returns the number of users of the
				997	value.<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	998	<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]	999	<tt>use_iterator use_begin()</tt> - Get an iterator to the start of
				1000	the use-list.<br>
				1001	<tt>use_iterator use_end()</tt> - Get an iterator to the end of the
				1002	use-list.<br>
				1003	<tt><a href="#User">User</a> *use_back()</tt> - Returns the last
				1004	element in the list.
				1005	<p> These methods are the interface to access the def-use
				1006	information in LLVM. As with all other iterators in LLVM, the naming
				1007	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]	1008	</li>
				1009	<li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1010	<p>This method returns the Type of the Value.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1011	</li>
				1012	<li><tt>bool hasName() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1013	<tt>std::string getName() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1014	<tt>void setName(const std::string &Name)</tt>
				1015	<p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
				1016	be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1017	</li>
				1018	<li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1019
				1020	<p>This method traverses the use list of a <tt>Value</tt> changing all <a
				1021	href="#User"><tt>User</tt>s</a> of the current value to refer to
				1022	"<tt>V</tt>" instead. For example, if you detect that an instruction always
				1023	produces a constant value (for example through constant folding), you can
				1024	replace all uses of the instruction with the constant like this:</p>
				1025
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1026	<pre> Inst->replaceAllUsesWith(ConstVal);<br></pre>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1027	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1028
				1029	</div>
				1030
				1031	<!-- ======================================================================= -->
				1032	<div class="doc_subsection">
				1033	<a name="User">The <tt>User</tt> class</a>
				1034	</div>
				1035
				1036	<div class="doc_text">
				1037
				1038	<p>
				1039	<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1040	doxygen info: <a href="/doxygen/classUser.html">User Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1041	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1042
				1043	<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
				1044	refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
				1045	that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
				1046	referring to. The <tt>User</tt> class itself is a subclass of
				1047	<tt>Value</tt>.</p>
				1048
				1049	<p>The operands of a <tt>User</tt> point directly to the LLVM <a
				1050	href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
				1051	Single Assignment (SSA) form, there can only be one definition referred to,
				1052	allowing this direct connection. This connection provides the use-def
				1053	information in LLVM.</p>
				1054
				1055	</div>
				1056
				1057	<!-- _______________________________________________________________________ -->
				1058	<div class="doc_subsubsection">
				1059	<a name="m_User">Important Public Members of the <tt>User</tt> class</a>
				1060	</div>
				1061
				1062	<div class="doc_text">
				1063
				1064	<p>The <tt>User</tt> class exposes the operand list in two ways: through
				1065	an index access interface and through an iterator based interface.</p>
				1066
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1067	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1068	<li><tt>Value *getOperand(unsigned i)</tt><br>
				1069	<tt>unsigned getNumOperands()</tt>
				1070	<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]	1071	convenient form for direct access.</p></li>
				1072
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1073	<li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
				1074	list<br>
				1075	<tt>User::op_const_iterator</tt> <tt>use_iterator op_begin()</tt> -
				1076	Get an iterator to the start of the operand list.<br>
				1077	<tt>use_iterator op_end()</tt> - Get an iterator to the end of the
				1078	operand list.
				1079	<p> Together, these methods make up the iterator based interface to
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1080	the operands of a <tt>User</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1081	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1082
				1083	</div>
				1084
				1085	<!-- ======================================================================= -->
				1086	<div class="doc_subsection">
				1087	<a name="Instruction">The <tt>Instruction</tt> class</a>
				1088	</div>
				1089
				1090	<div class="doc_text">
				1091
				1092	<p><tt>#include "</tt><tt><a
				1093	href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
				1094	doxygen info: <a href="/doxygen/classInstruction.html">Instruction Class</a><br>
				1095	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1096	href="#Value"><tt>Value</tt></a></p>
				1097
				1098	<p>The <tt>Instruction</tt> class is the common base class for all LLVM
				1099	instructions. It provides only a few methods, but is a very commonly used
				1100	class. The primary data tracked by the <tt>Instruction</tt> class itself is the
				1101	opcode (instruction type) and the parent <a
				1102	href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
				1103	into. To represent a specific type of instruction, one of many subclasses of
				1104	<tt>Instruction</tt> are used.</p>
				1105
				1106	<p> Because the <tt>Instruction</tt> class subclasses the <a
				1107	href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
				1108	way as for other <a href="#User"><tt>User</tt></a>s (with the
				1109	<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
				1110	<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
				1111	the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
				1112	file contains some meta-data about the various different types of instructions
				1113	in LLVM. It describes the enum values that are used as opcodes (for example
				1114	<tt>Instruction::Add</tt> and <tt>Instruction::SetLE</tt>), as well as the
				1115	concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
				1116	example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
				1117	href="#SetCondInst">SetCondInst</a></tt>). Unfortunately, the use of macros in
				1118	this file confuses doxygen, so these enum values don't show up correctly in the
				1119	<a href="/doxygen/classInstruction.html">doxygen output</a>.</p>
				1120
				1121	</div>
				1122
				1123	<!-- _______________________________________________________________________ -->
				1124	<div class="doc_subsubsection">
				1125	<a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
				1126	class</a>
				1127	</div>
				1128
				1129	<div class="doc_text">
				1130
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1131	<ul>
				1132	<li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1133	<p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
				1134	this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1135	<li><tt>bool mayWriteToMemory()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1136	<p>Returns true if the instruction writes to memory, i.e. it is a
				1137	<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]	1138	<li><tt>unsigned getOpcode()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1139	<p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1140	<li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1141	<p>Returns another instance of the specified instruction, identical
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1142	in all ways to the original except that the instruction has no parent
				1143	(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]	1144	and it has no name</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1145	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1146
				1147	</div>
				1148
				1149	<!-- ======================================================================= -->
				1150	<div class="doc_subsection">
				1151	<a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
				1152	</div>
				1153
				1154	<div class="doc_text">
				1155
				1156	<p><tt>#include "<a href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1157	doxygen info: <a href="/doxygen/classBasicBlock.html">BasicBlock Class</a><br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1158	Superclass: <a href="#Value"><tt>Value</tt></a></p>
				1159
				1160	<p>This class represents a single entry multiple exit section of the code,
				1161	commonly known as a basic block by the compiler community. The
				1162	<tt>BasicBlock</tt> class maintains a list of <a
				1163	href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
				1164	Matching the language definition, the last element of this list of instructions
				1165	is always a terminator instruction (a subclass of the <a
				1166	href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
				1167
				1168	<p>In addition to tracking the list of instructions that make up the block, the
				1169	<tt>BasicBlock</tt> class also keeps track of the <a
				1170	href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
				1171
				1172	<p>Note that <tt>BasicBlock</tt>s themselves are <a
				1173	href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
				1174	like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
				1175	<tt>label</tt>.</p>
				1176
				1177	</div>
				1178
				1179	<!-- _______________________________________________________________________ -->
				1180	<div class="doc_subsubsection">
				1181	<a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
				1182	class</a>
				1183	</div>
				1184
				1185	<div class="doc_text">
				1186
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1187	<ul>
				1188	<li><tt>BasicBlock(const std::string &Name = "", </tt><tt><a
				1189	href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1190	<p>The <tt>BasicBlock</tt> constructor is used to create new basic
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1191	blocks for insertion into a function. The constructor optionally takes
				1192	a name for the new block, and a <a href="#Function"><tt>Function</tt></a>
				1193	to insert it into. If the <tt>Parent</tt> parameter is specified, the
				1194	new <tt>BasicBlock</tt> is automatically inserted at the end of the
				1195	specified <a href="#Function"><tt>Function</tt></a>, if not specified,
				1196	the BasicBlock must be manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1197	</li>
				1198	<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list
				1199	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1200	<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1201	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,<tt>size()</tt>,<tt>empty()</tt>,<tt>rbegin()</tt>,<tt>rend()
				1202	- </tt>STL style functions for accessing the instruction list.
				1203	<p> These methods and typedefs are forwarding functions that have
				1204	the same semantics as the standard library methods of the same names.
				1205	These methods expose the underlying instruction list of a basic block in
				1206	a way that is easy to manipulate. To get the full complement of
				1207	container operations (including operations to update the list), you must
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1208	use the <tt>getInstList()</tt> method.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1209	<li><tt>BasicBlock::InstListType &getInstList()</tt>
				1210	<p> This method is used to get access to the underlying container
				1211	that actually holds the Instructions. This method must be used when
				1212	there isn't a forwarding function in the <tt>BasicBlock</tt> class for
				1213	the operation that you would like to perform. Because there are no
				1214	forwarding functions for "updating" operations, you need to use this if
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1215	you want to update the contents of a <tt>BasicBlock</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1216	<li><tt><a href="#Function">Function</a> *getParent()</tt>
				1217	<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1218	the block is embedded into, or a null pointer if it is homeless.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1219	<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
				1220	<p> Returns a pointer to the terminator instruction that appears at
				1221	the end of the <tt>BasicBlock</tt>. If there is no terminator
				1222	instruction, or if the last instruction in the block is not a
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1223	terminator, then a null pointer is returned.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1224	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1225
				1226	</div>
				1227
				1228	<!-- ======================================================================= -->
				1229	<div class="doc_subsection">
				1230	<a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
				1231	</div>
				1232
				1233	<div class="doc_text">
				1234
				1235	<p><tt>#include "<a
				1236	href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
				1237	doxygen info: <a href="/doxygen/classGlobalValue.html">GlobalValue Class</a><br>
				1238	Superclasses: <a href="#User"><tt>User</tt></a>, <a
				1239	href="#Value"><tt>Value</tt></a></p>
				1240
				1241	<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
				1242	href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
				1243	visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
				1244	Because they are visible at global scope, they are also subject to linking with
				1245	other globals defined in different translation units. To control the linking
				1246	process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
				1247	<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
				1248	defined by the <tt>LinkageTypes</tt> enumerator.</p>
				1249
				1250	<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
				1251	<tt>static</tt> in C), it is not visible to code outside the current translation
				1252	unit, and does not participate in linking. If it has external linkage, it is
				1253	visible to external code, and does participate in linking. In addition to
				1254	linkage information, <tt>GlobalValue</tt>s keep track of which <a
				1255	href="#Module"><tt>Module</tt></a> they are currently part of.</p>
				1256
				1257	<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
				1258	by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
				1259	global is always a pointer to its contents. It is important to remember this
				1260	when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
				1261	be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
				1262	subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
				1263	int]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
				1264	the address of the first element of this array and the value of the
				1265	<tt>GlobalVariable</tt> are the same, they have different types. The
				1266	<tt>GlobalVariable</tt>'s type is <tt>[24 x int]</tt>. The first element's type
				1267	is <tt>int.</tt> Because of this, accessing a global value requires you to
				1268	dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
				1269	can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
				1270	Language Reference Manual</a>.</p>
				1271
				1272	</div>
				1273
				1274	<!-- _______________________________________________________________________ -->
				1275	<div class="doc_subsubsection">
				1276	<a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
				1277	class</a>
				1278	</div>
				1279
				1280	<div class="doc_text">
				1281
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1282	<ul>
				1283	<li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1284	<tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1285	<tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
				1286	<p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
				1287	<p> </p>
				1288	</li>
				1289	<li><tt><a href="#Module">Module</a> *getParent()</tt>
				1290	<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]	1291	GlobalValue is currently embedded into.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1292	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1293
				1294	</div>
				1295
				1296	<!-- ======================================================================= -->
				1297	<div class="doc_subsection">
				1298	<a name="Function">The <tt>Function</tt> class</a>
				1299	</div>
				1300
				1301	<div class="doc_text">
				1302
				1303	<p><tt>#include "<a
				1304	href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
				1305	info: <a href="/doxygen/classFunction.html">Function Class</a><br> Superclasses:
				1306	<a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1307	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1308
				1309	<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
				1310	actually one of the more complex classes in the LLVM heirarchy because it must
				1311	keep track of a large amount of data. The <tt>Function</tt> class keeps track
				1312	of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal <a
				1313	href="#Argument"><tt>Argument</tt></a>s, and a <a
				1314	href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
				1315
				1316	<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
				1317	commonly used part of <tt>Function</tt> objects. The list imposes an implicit
				1318	ordering of the blocks in the function, which indicate how the code will be
				1319	layed out by the backend. Additionally, the first <a
				1320	href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
				1321	<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
				1322	block. There are no implicit exit nodes, and in fact there may be multiple exit
				1323	nodes from a single <tt>Function</tt>. If the <a
				1324	href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
				1325	the <tt>Function</tt> is actually a function declaration: the actual body of the
				1326	function hasn't been linked in yet.</p>
				1327
				1328	<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
				1329	<tt>Function</tt> class also keeps track of the list of formal <a
				1330	href="#Argument"><tt>Argument</tt></a>s that the function receives. This
				1331	container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
				1332	nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
				1333	the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
				1334
				1335	<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
				1336	LLVM feature that is only used when you have to look up a value by name. Aside
				1337	from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
				1338	internally to make sure that there are not conflicts between the names of <a
				1339	href="#Instruction"><tt>Instruction</tt></a>s, <a
				1340	href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
				1341	href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
				1342
				1343	</div>
				1344
				1345	<!-- _______________________________________________________________________ -->
				1346	<div class="doc_subsubsection">
				1347	<a name="m_Function">Important Public Members of the <tt>Function</tt>
				1348	class</a>
				1349	</div>
				1350
				1351	<div class="doc_text">
				1352
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1353	<ul>
				1354	<li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1355	Ty, bool isInternal, const std::string &N = "", Module Parent = 0)</tt>
				1356
				1357	<p>Constructor used when you need to create new <tt>Function</tt>s to add
				1358	the the program. The constructor must specify the type of the function to
				1359	create and whether or not it should start out with internal or external
				1360	linkage. The <a href="#FunctionType"><tt>FunctionType</tt></a> argument
				1361	specifies the formal arguments and return value for the function. The same
				1362	<a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
				1363	create multiple functions. The <tt>Parent</tt> argument specifies the Module
				1364	in which the function is defined. If this argument is provided, the function
				1365	will automatically be inserted into that module's list of
				1366	functions.</p></li>
				1367
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1368	<li><tt>bool isExternal()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1369
				1370	<p>Return whether or not the <tt>Function</tt> has a body defined. If the
				1371	function is "external", it does not have a body, and thus must be resolved
				1372	by linking with a function defined in a different translation unit.</p></li>
				1373
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1374	<li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1375	<tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1376
				1377	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1378	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1379
				1380	<p>These are forwarding methods that make it easy to access the contents of
				1381	a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
				1382	list.</p></li>
				1383
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1384	<li><tt>Function::BasicBlockListType &getBasicBlockList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1385
				1386	<p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
				1387	is necessary to use when you need to update the list or perform a complex
				1388	action that doesn't have a forwarding method.</p></li>
				1389
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1390	<li><tt>Function::aiterator</tt> - Typedef for the argument list
				1391	iterator<br>
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1392	<tt>Function::const_aiterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1393
				1394	<tt>abegin()</tt>, <tt>aend()</tt>, <tt>afront()</tt>, <tt>aback()</tt>,
				1395	<tt>asize()</tt>, <tt>aempty()</tt>, <tt>arbegin()</tt>, <tt>arend()</tt>
				1396
				1397	<p>These are forwarding methods that make it easy to access the contents of
				1398	a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
				1399	list.</p></li>
				1400
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1401	<li><tt>Function::ArgumentListType &getArgumentList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1402
				1403	<p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
				1404	necessary to use when you need to update the list or perform a complex
				1405	action that doesn't have a forwarding method.</p></li>
				1406
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1407	<li><tt><a href="#BasicBlock">BasicBlock</a> &getEntryBlock()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1408
				1409	<p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
				1410	function. Because the entry block for the function is always the first
				1411	block, this returns the first block of the <tt>Function</tt>.</p></li>
				1412
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1413	<li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
				1414	<tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1415
				1416	<p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
				1417	<tt>Function</tt> and returns the return type of the function, or the <a
				1418	href="#FunctionType"><tt>FunctionType</tt></a> of the actual
				1419	function.</p></li>
				1420
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1421	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1422
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1423	<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]	1424	for this <tt>Function</tt>.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1425	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1426
				1427	</div>
				1428
				1429	<!-- ======================================================================= -->
				1430	<div class="doc_subsection">
				1431	<a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
				1432	</div>
				1433
				1434	<div class="doc_text">
				1435
				1436	<p><tt>#include "<a
				1437	href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
				1438	<br>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1439	doxygen info: <a href="/doxygen/classGlobalVariable.html">GlobalVariable
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1440	Class</a><br> Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>, <a
				1441	href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
				1442
				1443	<p>Global variables are represented with the (suprise suprise)
				1444	<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
				1445	subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
				1446	always referenced by their address (global values must live in memory, so their
				1447	"name" refers to their address). See <a
				1448	href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global variables
				1449	may have an initial value (which must be a <a
				1450	href="#Constant"><tt>Constant</tt></a>), and if they have an initializer, they
				1451	may be marked as "constant" themselves (indicating that their contents never
				1452	change at runtime).</p>
				1453
				1454	</div>
				1455
				1456	<!-- _______________________________________________________________________ -->
				1457	<div class="doc_subsubsection">
				1458	<a name="m_GlobalVariable">Important Public Members of the
				1459	<tt>GlobalVariable</tt> class</a>
				1460	</div>
				1461
				1462	<div class="doc_text">
				1463
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1464	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1465	<li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
				1466	isConstant, LinkageTypes& Linkage, <a href="#Constant">Constant</a>
				1467	Initializer = 0, const std::string &Name = "", Module Parent = 0)</tt>
				1468
				1469	<p>Create a new global variable of the specified type. If
				1470	<tt>isConstant</tt> is true then the global variable will be marked as
				1471	unchanging for the program. The Linkage parameter specifies the type of
				1472	linkage (internal, external, weak, linkonce, appending) for the variable. If
				1473	the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,  then
				1474	the resultant global variable will have internal linkage. AppendingLinkage
				1475	concatenates together all instances (in different translation units) of the
				1476	variable into a single variable but is only applicable to arrays.  See
				1477	the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
				1478	further details on linkage types. Optionally an initializer, a name, and the
				1479	module to put the variable into may be specified for the global variable as
				1480	well.</p></li>
				1481
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1482	<li><tt>bool isConstant() const</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1483
				1484	<p>Returns true if this is a global variable that is known not to
				1485	be modified at runtime.</p></li>
				1486
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1487	<li><tt>bool hasInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1488
				1489	<p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
				1490
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1491	<li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1492
				1493	<p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
				1494	to call this method if there is no initializer.</p></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1495	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1496
				1497	</div>
				1498
				1499	<!-- ======================================================================= -->
				1500	<div class="doc_subsection">
				1501	<a name="Module">The <tt>Module</tt> class</a>
				1502	</div>
				1503
				1504	<div class="doc_text">
				1505
				1506	<p><tt>#include "<a
				1507	href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
				1508	<a href="/doxygen/classModule.html">Module Class</a></p>
				1509
				1510	<p>The <tt>Module</tt> class represents the top level structure present in LLVM
				1511	programs. An LLVM module is effectively either a translation unit of the
				1512	original program or a combination of several translation units merged by the
				1513	linker. The <tt>Module</tt> class keeps track of a list of <a
				1514	href="#Function"><tt>Function</tt></a>s, a list of <a
				1515	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
				1516	href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
				1517	helpful member functions that try to make common operations easy.</p>
				1518
				1519	</div>
				1520
				1521	<!-- _______________________________________________________________________ -->
				1522	<div class="doc_subsubsection">
				1523	<a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
				1524	</div>
				1525
				1526	<div class="doc_text">
				1527
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1528	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1529	<li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1530	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1531
				1532	<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
				1533	provide a name for it (probably based on the name of the translation unit).</p>
				1534
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1535	<ul>
				1536	<li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner	0377de4	2002-09-06 14:50:55 +0000	[diff] [blame]	1537	<tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1538
				1539	<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
				1540	<tt>size()</tt>, <tt>empty()</tt>, <tt>rbegin()</tt>, <tt>rend()</tt>
				1541
				1542	<p>These are forwarding methods that make it easy to access the contents of
				1543	a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
				1544	list.</p></li>
				1545
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1546	<li><tt>Module::FunctionListType &getFunctionList()</tt>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1547
				1548	<p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
				1549	necessary to use when you need to update the list or perform a complex
				1550	action that doesn't have a forwarding method.</p>
				1551
				1552	<p><!-- Global Variable --></p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1553	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1554
				1555	<hr>
				1556
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1557	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1558	<li><tt>Module::giterator</tt> - Typedef for global variable list iterator<br>
				1559
				1560	<tt>Module::const_giterator</tt> - Typedef for const_iterator.<br>
				1561
				1562	<tt>gbegin()</tt>, <tt>gend()</tt>, <tt>gfront()</tt>, <tt>gback()</tt>,
				1563	<tt>gsize()</tt>, <tt>gempty()</tt>, <tt>grbegin()</tt>, <tt>grend()</tt>
				1564
				1565	<p> These are forwarding methods that make it easy to access the contents of
				1566	a <tt>Module</tt> object's <a
				1567	href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
				1568
				1569	<li><tt>Module::GlobalListType &getGlobalList()</tt>
				1570
				1571	<p>Returns the list of <a
				1572	href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
				1573	use when you need to update the list or perform a complex action that
				1574	doesn't have a forwarding method.</p>
				1575
				1576	<p><!-- Symbol table stuff --> </p></li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1577	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1578
				1579	<hr>
				1580
				1581	<ul>
				1582	<li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
				1583
				1584	<p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1585	for this <tt>Module</tt>.</p>
				1586
				1587	<p><!-- Convenience methods --></p></li>
				1588	</ul>
				1589
				1590	<hr>
				1591
				1592	<ul>
				1593	<li><tt><a href="#Function">Function</a> *getFunction(const std::string
				1594	&Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
				1595
				1596	<p>Look up the specified function in the <tt>Module</tt> <a
				1597	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
				1598	<tt>null</tt>.</p></li>
				1599
				1600	<li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
				1601	std::string &Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
				1602
				1603	<p>Look up the specified function in the <tt>Module</tt> <a
				1604	href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
				1605	external declaration for the function and return it.</p></li>
				1606
				1607	<li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
				1608
				1609	<p>If there is at least one entry in the <a
				1610	href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
				1611	href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
				1612	string.</p></li>
				1613
				1614	<li><tt>bool addTypeName(const std::string &Name, const <a
				1615	href="#Type">Type</a> *Ty)</tt>
				1616
				1617	<p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
				1618	mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
				1619	name, true is returned and the <a
				1620	href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
				1621	</ul>
				1622
				1623	</div>
				1624
				1625	<!-- ======================================================================= -->
				1626	<div class="doc_subsection">
				1627	<a name="Constant">The <tt>Constant</tt> class and subclasses</a>
				1628	</div>
				1629
				1630	<div class="doc_text">
				1631
				1632	<p>Constant represents a base class for different types of constants. It
				1633	is subclassed by ConstantBool, ConstantInt, ConstantSInt, ConstantUInt,
				1634	ConstantArray etc for representing the various types of Constants.</p>
				1635
				1636	</div>
				1637
				1638	<!-- _______________________________________________________________________ -->
				1639	<div class="doc_subsubsection">
				1640	<a name="m_Value">Important Public Methods</a>
				1641	</div>
				1642
				1643	<div class="doc_text">
				1644
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1645	<ul>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1646	<li><tt>bool isConstantExpr()</tt>: Returns true if it is a
				1647	ConstantExpr
				1648	<hr> Important Subclasses of Constant
				1649	<p> </p>
				1650	<ul>
				1651	<li>ConstantSInt : This subclass of Constant represents a signed
				1652	integer constant.
				1653	<ul>
				1654	<li><tt>int64_t getValue() const</tt>: Returns the underlying value of
				1655	this constant. </li>
				1656	</ul>
				1657	</li>
				1658	<li>ConstantUInt : This class represents an unsigned integer.
				1659	<ul>
				1660	<li><tt>uint64_t getValue() const</tt>: Returns the underlying value
				1661	of this constant. </li>
				1662	</ul>
				1663	</li>
				1664	<li>ConstantFP : This class represents a floating point constant.
				1665	<ul>
				1666	<li><tt>double getValue() const</tt>: Returns the underlying value of
				1667	this constant. </li>
				1668	</ul>
				1669	</li>
				1670	<li>ConstantBool : This represents a boolean constant.
				1671	<ul>
				1672	<li><tt>bool getValue() const</tt>: Returns the underlying value of
				1673	this constant. </li>
				1674	</ul>
				1675	</li>
				1676	<li>ConstantArray : This represents a constant array.
				1677	<ul>
				1678	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1679	Returns a Vecotr of component constants that makeup this array. </li>
				1680	</ul>
				1681	</li>
				1682	<li>ConstantStruct : This represents a constant struct.
				1683	<ul>
				1684	<li><tt>const std::vector<Use> &getValues() const</tt>:
				1685	Returns a Vecotr of component constants that makeup this array. </li>
				1686	</ul>
				1687	</li>
				1688	<li>ConstantPointerRef : This represents a constant pointer value
				1689	that is initialized to point to a global value, which lies at a
				1690	constant fixed address.
				1691	<ul>
				1692	<li><tt>GlobalValue *getValue()</tt>: Returns the global
				1693	value to which this pointer is pointing to. </li>
				1694	</ul>
				1695	</li>
				1696	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1697	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1698	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1699
				1700	</div>
				1701
				1702	<!-- ======================================================================= -->
				1703	<div class="doc_subsection">
				1704	<a name="Type">The <tt>Type</tt> class and Derived Types</a>
				1705	</div>
				1706
				1707	<div class="doc_text">
				1708
				1709	<p>Type as noted earlier is also a subclass of a Value class. Any primitive
				1710	type (like int, short etc) in LLVM is an instance of Type Class. All other
				1711	types are instances of subclasses of type like FunctionType, ArrayType
				1712	etc. DerivedType is the interface for all such dervied types including
				1713	FunctionType, ArrayType, PointerType, StructType. Types can have names. They can
				1714	be recursive (StructType). There exists exactly one instance of any type
				1715	structure at a time. This allows using pointer equality of Type *s for comparing
				1716	types.</p>
				1717
				1718	</div>
				1719
				1720	<!-- _______________________________________________________________________ -->
				1721	<div class="doc_subsubsection">
				1722	<a name="m_Value">Important Public Methods</a>
				1723	</div>
				1724
				1725	<div class="doc_text">
				1726
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1727	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1728
				1729	<li><tt>PrimitiveID getPrimitiveID() const</tt>: Returns the base type of the
				1730	type.</li>
				1731
				1732	<li><tt>bool isSigned() const</tt>: Returns whether an integral numeric type
				1733	is signed. This is true for SByteTy, ShortTy, IntTy, LongTy. Note that this is
				1734	not true for Float and Double. </li>
				1735
				1736	<li><tt>bool isUnsigned() const</tt>: Returns whether a numeric type is
				1737	unsigned. This is not quite the complement of isSigned... nonnumeric types
				1738	return false as they do with isSigned. This returns true for UByteTy,
				1739	UShortTy, UIntTy, and ULongTy. </li>
				1740
				1741	<li><tt>bool isInteger() const</tt>: Equilivent to isSigned() \|\| isUnsigned(),
				1742	but with only a single virtual function invocation.</li>
				1743
				1744	<li><tt>bool isIntegral() const</tt>: Returns true if this is an integral
				1745	type, which is either Bool type or one of the Integer types.</li>
				1746
				1747	<li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
				1748	floating point types.</li>
				1749
				1750	<li><tt>bool isRecursive() const</tt>: Returns rue if the type graph contains
				1751	a cycle.</li>
				1752
				1753	<li><tt>isLosslesslyConvertableTo (const Type *Ty) const</tt>: Return true if
				1754	this type can be converted to 'Ty' without any reinterpretation of bits. For
				1755	example, uint to int.</li>
				1756
				1757	<li><tt>bool isPrimitiveType() const</tt>: Returns true if it is a primitive
				1758	type.</li>
				1759
				1760	<li><tt>bool isDerivedType() const</tt>: Returns true if it is a derived
				1761	type.</li>
				1762
				1763	<li><tt>const Type * getContainedType (unsigned i) const</tt>: This method is
				1764	used to implement the type iterator. For derived types, this returns the types
				1765	'contained' in the derived type, returning 0 when 'i' becomes invalid. This
				1766	allows the user to iterate over the types in a struct, for example, really
				1767	easily.</li>
				1768
				1769	<li><tt>unsigned getNumContainedTypes() const</tt>: Return the number of types
				1770	in the derived type.
				1771
				1772	<hr>
				1773	<p>Derived Types</p>
				1774
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1775	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1776	<li>SequentialType : This is subclassed by ArrayType and PointerType
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1777	<ul>
				1778	<li><tt>const Type * getElementType() const</tt>: Returns the type of
				1779	each of the elements in the sequential type. </li>
				1780	</ul>
				1781	</li>
				1782	<li>ArrayType : This is a subclass of SequentialType and defines
				1783	interface for array types.
				1784	<ul>
				1785	<li><tt>unsigned getNumElements() const</tt>: Returns the number of
				1786	elements in the array. </li>
				1787	</ul>
				1788	</li>
				1789	<li>PointerType : Subclass of SequentialType for pointer types. </li>
				1790	<li>StructType : subclass of DerivedTypes for struct types </li>
				1791	<li>FunctionType : subclass of DerivedTypes for function types.
				1792	<ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1793	<li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
				1794	function</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1795	<li><tt> const Type * getReturnType() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1796	return type of the function.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1797	<li><tt>const Type * getParamType (unsigned i)</tt>: Returns
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1798	the type of the ith parameter.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1799	<li><tt> const unsigned getNumParams() const</tt>: Returns the
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1800	number of formal parameters.</li>
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1801	</ul>
				1802	</li>
				1803	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1804	</li>
Chris Lattner	c75ff9a	2002-10-01 23:17:09 +0000	[diff] [blame]	1805	</ul>
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1806
				1807	</div>
				1808
				1809	<!-- ======================================================================= -->
				1810	<div class="doc_subsection">
				1811	<a name="Argument">The <tt>Argument</tt> class</a>
				1812	</div>
				1813
				1814	<div class="doc_text">
				1815
				1816	<p>This subclass of Value defines the interface for incoming formal
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1817	arguments to a function. A Function maitanis a list of its formal
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1818	arguments. An argument has a pointer to the parent Function.</p>
				1819
				1820	</div>
				1821
Chris Lattner	9355b47	2002-09-06 02:50:58 +0000	[diff] [blame]	1822	<!-- *********************************************************************** -->
Misha Brukman	13fd15c	2004-01-15 00:14:41 +0000	[diff] [blame]	1823	<hr>
				1824	<address>
				1825	<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
				1826	src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
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				1829
				1830	<a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
				1831	<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
				1832	<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
				1833	Last modified: $Date$
				1834	</address>
				1835
Chris Lattner	261efe9	2003-11-25 01:02:51 +0000	[diff] [blame]	1836	</body>
				1837	</html>