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4<head>
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Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]6 <title>LLVM Programmer's Manual</title>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]7 <link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]8</head>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]9<body>
10
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]11<h1>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]12 LLVM Programmer's Manual
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]13</h1>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]14
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]15<ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]16 <li><a href="#introduction">Introduction</a></li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]17 <li><a href="#general">General Information</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]18 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]19 <li><a href="#stl">The C++ Standard Template Library</a></li>
20<!--
21 <li>The <tt>-time-passes</tt> option</li>
22 <li>How to use the LLVM Makefile system</li>
23 <li>How to write a regression test</li>
Chris Lattner61db4652004-12-08 19:05:44 +0000[diff] [blame]24
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]25-->
Chris Lattner84b7f8d2003-08-01 22:20:59 +0000[diff] [blame]26 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]27 </li>
28 <li><a href="#apis">Important and useful LLVM APIs</a>
29 <ul>
30 <li><a href="#isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt>
31and <tt>dyn_cast&lt;&gt;</tt> templates</a> </li>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]32 <li><a href="#string_apis">Passing strings (the <tt>StringRef</tt>
Benjamin Kramere15192b2009-08-05 15:42:44 +0000[diff] [blame]33and <tt>Twine</tt> classes)</a>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]34 <ul>
35 <li><a href="#StringRef">The <tt>StringRef</tt> class</a> </li>
36 <li><a href="#Twine">The <tt>Twine</tt> class</a> </li>
37 </ul>
Benjamin Kramere15192b2009-08-05 15:42:44 +0000[diff] [blame]38 </li>
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]39 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]40option</a>
41 <ul>
42 <li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
43and the <tt>-debug-only</tt> option</a> </li>
44 </ul>
45 </li>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]46 <li><a href="#Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]47option</a></li>
48<!--
49 <li>The <tt>InstVisitor</tt> template
50 <li>The general graph API
51-->
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]52 <li><a href="#ViewGraph">Viewing graphs while debugging code</a></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]53 </ul>
54 </li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]55 <li><a href="#datastructure">Picking the Right Data Structure for a Task</a>
56 <ul>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]57 <li><a href="#ds_sequential">Sequential Containers (std::vector, std::list, etc)</a>
58 <ul>
Chris Lattner8ae42612011-04-05 23:18:20 +0000[diff] [blame]59 <li><a href="#dss_arrayref">llvm/ADT/ArrayRef.h</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]60 <li><a href="#dss_fixedarrays">Fixed Size Arrays</a></li>
61 <li><a href="#dss_heaparrays">Heap Allocated Arrays</a></li>
Chris Lattner9d69d4a2011-07-18 01:40:02 +0000[diff] [blame]62 <li><a href="#dss_tinyptrvector">"llvm/ADT/TinyPtrVector.h"</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]63 <li><a href="#dss_smallvector">"llvm/ADT/SmallVector.h"</a></li>
64 <li><a href="#dss_vector">&lt;vector&gt;</a></li>
65 <li><a href="#dss_deque">&lt;deque&gt;</a></li>
66 <li><a href="#dss_list">&lt;list&gt;</a></li>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]67 <li><a href="#dss_ilist">llvm/ADT/ilist.h</a></li>
Argyrios Kyrtzidis81df0892011-06-15 19:56:01 +0000[diff] [blame]68 <li><a href="#dss_packedvector">llvm/ADT/PackedVector.h</a></li>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]69 <li><a href="#dss_other">Other Sequential Container Options</a></li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]70 </ul></li>
Chris Lattner7314a202011-07-22 20:46:49 +0000[diff] [blame]71 <li><a href="#ds_string">String-like containers</a>
72 <!--<ul>
73 todo
74 </ul>--></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]75 <li><a href="#ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
76 <ul>
77 <li><a href="#dss_sortedvectorset">A sorted 'vector'</a></li>
78 <li><a href="#dss_smallset">"llvm/ADT/SmallSet.h"</a></li>
79 <li><a href="#dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a></li>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]80 <li><a href="#dss_denseset">"llvm/ADT/DenseSet.h"</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]81 <li><a href="#dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a></li>
82 <li><a href="#dss_set">&lt;set&gt;</a></li>
83 <li><a href="#dss_setvector">"llvm/ADT/SetVector.h"</a></li>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]84 <li><a href="#dss_uniquevector">"llvm/ADT/UniqueVector.h"</a></li>
85 <li><a href="#dss_otherset">Other Set-Like ContainerOptions</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]86 </ul></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]87 <li><a href="#ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
88 <ul>
89 <li><a href="#dss_sortedvectormap">A sorted 'vector'</a></li>
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]90 <li><a href="#dss_stringmap">"llvm/ADT/StringMap.h"</a></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]91 <li><a href="#dss_indexedmap">"llvm/ADT/IndexedMap.h"</a></li>
92 <li><a href="#dss_densemap">"llvm/ADT/DenseMap.h"</a></li>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]93 <li><a href="#dss_valuemap">"llvm/ADT/ValueMap.h"</a></li>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]94 <li><a href="#dss_intervalmap">"llvm/ADT/IntervalMap.h"</a></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]95 <li><a href="#dss_map">&lt;map&gt;</a></li>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]96 <li><a href="#dss_inteqclasses">"llvm/ADT/IntEqClasses.h"</a></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]97 <li><a href="#dss_othermap">Other Map-Like Container Options</a></li>
98 </ul></li>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]99 <li><a href="#ds_bit">BitVector-like containers</a>
100 <ul>
101 <li><a href="#dss_bitvector">A dense bitvector</a></li>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]102 <li><a href="#dss_smallbitvector">A "small" dense bitvector</a></li>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]103 <li><a href="#dss_sparsebitvector">A sparse bitvector</a></li>
104 </ul></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]105 </ul>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]106 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]107 <li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]108 <ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]109 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
110 <ul>
111 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
112in a <tt>Function</tt></a> </li>
113 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
114in a <tt>BasicBlock</tt></a> </li>
115 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
116in a <tt>Function</tt></a> </li>
117 <li><a href="#iterate_convert">Turning an iterator into a
118class pointer</a> </li>
119 <li><a href="#iterate_complex">Finding call sites: a more
120complex example</a> </li>
121 <li><a href="#calls_and_invokes">Treating calls and invokes
122the same way</a> </li>
123 <li><a href="#iterate_chains">Iterating over def-use &amp;
124use-def chains</a> </li>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]125 <li><a href="#iterate_preds">Iterating over predecessors &amp;
126successors of blocks</a></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]127 </ul>
128 </li>
129 <li><a href="#simplechanges">Making simple changes</a>
130 <ul>
131 <li><a href="#schanges_creating">Creating and inserting new
132 <tt>Instruction</tt>s</a> </li>
133 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
134 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
135with another <tt>Value</tt></a> </li>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]136 <li><a href="#schanges_deletingGV">Deleting <tt>GlobalVariable</tt>s</a> </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]137 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]138 </li>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]139 <li><a href="#create_types">How to Create Types</a></li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]140<!--
141 <li>Working with the Control Flow Graph
142 <ul>
143 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
144 <li>
145 <li>
146 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]147-->
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]148 </ul>
149 </li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]150
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]151 <li><a href="#threading">Threads and LLVM</a>
152 <ul>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]153 <li><a href="#startmultithreaded">Entering and Exiting Multithreaded Mode
154 </a></li>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]155 <li><a href="#shutdown">Ending execution with <tt>llvm_shutdown()</tt></a></li>
156 <li><a href="#managedstatic">Lazy initialization with <tt>ManagedStatic</tt></a></li>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]157 <li><a href="#llvmcontext">Achieving Isolation with <tt>LLVMContext</tt></a></li>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]158 <li><a href="#jitthreading">Threads and the JIT</a></li>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]159 </ul>
160 </li>
161
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]162 <li><a href="#advanced">Advanced Topics</a>
163 <ul>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]164
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]165 <li><a href="#SymbolTable">The <tt>ValueSymbolTable</tt> class</a></li>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]166 <li><a href="#UserLayout">The <tt>User</tt> and owned <tt>Use</tt> classes' memory layout</a></li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]167 </ul></li>
168
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]169 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]170 <ul>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]171 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]172 <li><a href="#Module">The <tt>Module</tt> class</a></li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]173 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]174 <ul>
175 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]176 <ul>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]177 <li><a href="#Instruction">The <tt>Instruction</tt> class</a></li>
178 <li><a href="#Constant">The <tt>Constant</tt> class</a>
179 <ul>
180 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]181 <ul>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]182 <li><a href="#Function">The <tt>Function</tt> class</a></li>
183 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
184 </ul>
185 </li>
186 </ul>
187 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]188 </ul>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]189 </li>
190 <li><a href="#BasicBlock">The <tt>BasicBlock</tt> class</a></li>
191 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
192 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]193 </li>
194 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]195 </li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]196</ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]197
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]198<div class="doc_author">
199 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner94c43592004-05-26 16:52:55 +0000[diff] [blame]200 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]201 <a href="mailto:ggreif@gmail.com">Gabor Greif</a>,
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]202 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>,
203 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a> and
204 <a href="mailto:owen@apple.com">Owen Anderson</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]205</div>
206
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]207<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]208<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]209 <a name="introduction">Introduction </a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]210</h2>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]211<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]212
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]213<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]214
215<p>This document is meant to highlight some of the important classes and
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]216interfaces available in the LLVM source-base. This manual is not
217intended to explain what LLVM is, how it works, and what LLVM code looks
218like. It assumes that you know the basics of LLVM and are interested
219in writing transformations or otherwise analyzing or manipulating the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]220code.</p>
221
222<p>This document should get you oriented so that you can find your
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]223way in the continuously growing source code that makes up the LLVM
224infrastructure. Note that this manual is not intended to serve as a
225replacement for reading the source code, so if you think there should be
226a method in one of these classes to do something, but it's not listed,
227check the source. Links to the <a href="/doxygen/">doxygen</a> sources
228are provided to make this as easy as possible.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]229
230<p>The first section of this document describes general information that is
231useful to know when working in the LLVM infrastructure, and the second describes
232the Core LLVM classes. In the future this manual will be extended with
233information describing how to use extension libraries, such as dominator
234information, CFG traversal routines, and useful utilities like the <tt><a
235href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
236
237</div>
238
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]239<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]240<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]241 <a name="general">General Information</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]242</h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]243<!-- *********************************************************************** -->
244
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]245<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]246
247<p>This section contains general information that is useful if you are working
248in the LLVM source-base, but that isn't specific to any particular API.</p>
249
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]250<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]251<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]252 <a name="stl">The C++ Standard Template Library</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]253</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]254
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]255<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]256
257<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]258perhaps much more than you are used to, or have seen before. Because of
259this, you might want to do a little background reading in the
260techniques used and capabilities of the library. There are many good
261pages that discuss the STL, and several books on the subject that you
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]262can get, so it will not be discussed in this document.</p>
263
264<p>Here are some useful links:</p>
265
266<ol>
267
Nick Lewyckyea1fe2c2010-10-09 21:12:29 +0000[diff] [blame]268<li><a href="http://www.dinkumware.com/manuals/#Standard C++ Library">Dinkumware
269C++ Library reference</a> - an excellent reference for the STL and other parts
270of the standard C++ library.</li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]271
272<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Gabor Greif0cbcabe2009-03-12 09:47:03 +0000[diff] [blame]273O'Reilly book in the making. It has a decent Standard Library
274Reference that rivals Dinkumware's, and is unfortunately no longer free since the
275book has been published.</li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]276
277<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
278Questions</a></li>
279
280<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
281Contains a useful <a
282href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
283STL</a>.</li>
284
285<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
286Page</a></li>
287
Tanya Lattner79445ba2004-12-08 18:34:56 +0000[diff] [blame]288<li><a href="http://64.78.49.204/">
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]289Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
290the book).</a></li>
291
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]292</ol>
293
294<p>You are also encouraged to take a look at the <a
295href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
296to write maintainable code more than where to put your curly braces.</p>
297
298</div>
299
300<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]301<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]302 <a name="stl">Other useful references</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]303</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]304
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]305<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]306
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]307<ol>
Misha Brukmana0f71e42004-06-18 18:39:00 +0000[diff] [blame]308<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
309static and shared libraries across platforms</a></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]310</ol>
311
312</div>
313
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]314</div>
315
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]316<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]317<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]318 <a name="apis">Important and useful LLVM APIs</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]319</h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]320<!-- *********************************************************************** -->
321
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]322<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]323
324<p>Here we highlight some LLVM APIs that are generally useful and good to
325know about when writing transformations.</p>
326
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]327<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]328<h3>
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]329 <a name="isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt> and
330 <tt>dyn_cast&lt;&gt;</tt> templates</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]331</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]332
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]333<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]334
335<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]336These templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
337operator, but they don't have some drawbacks (primarily stemming from
338the fact that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that
339have a v-table). Because they are used so often, you must know what they
340do and how they work. All of these templates are defined in the <a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]341 href="/doxygen/Casting_8h-source.html"><tt>llvm/Support/Casting.h</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]342file (note that you very rarely have to include this file directly).</p>
343
344<dl>
345 <dt><tt>isa&lt;&gt;</tt>: </dt>
346
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]347 <dd><p>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]348 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
349 a reference or pointer points to an instance of the specified class. This can
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]350 be very useful for constraint checking of various sorts (example below).</p>
351 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]352
353 <dt><tt>cast&lt;&gt;</tt>: </dt>
354
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]355 <dd><p>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
Chris Lattner28e6ff52008-06-20 05:03:17 +0000[diff] [blame]356 converts a pointer or reference from a base class to a derived class, causing
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]357 an assertion failure if it is not really an instance of the right type. This
358 should be used in cases where you have some information that makes you believe
359 that something is of the right type. An example of the <tt>isa&lt;&gt;</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]360 and <tt>cast&lt;&gt;</tt> template is:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]361
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]362<div class="doc_code">
363<pre>
364static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
365 if (isa&lt;<a href="#Constant">Constant</a>&gt;(V) || isa&lt;<a href="#Argument">Argument</a>&gt;(V) || isa&lt;<a href="#GlobalValue">GlobalValue</a>&gt;(V))
366 return true;
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]367
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]368 // <i>Otherwise, it must be an instruction...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]369 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
370}
371</pre>
372</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]373
374 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
375 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
376 operator.</p>
377
378 </dd>
379
380 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
381
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]382 <dd><p>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation.
383 It checks to see if the operand is of the specified type, and if so, returns a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]384 pointer to it (this operator does not work with references). If the operand is
385 not of the correct type, a null pointer is returned. Thus, this works very
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]386 much like the <tt>dynamic_cast&lt;&gt;</tt> operator in C++, and should be
387 used in the same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt>
388 operator is used in an <tt>if</tt> statement or some other flow control
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]389 statement like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]390
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]391<div class="doc_code">
392<pre>
393if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]394 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]395}
396</pre>
397</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]398
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]399 <p>This form of the <tt>if</tt> statement effectively combines together a call
400 to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
401 statement, which is very convenient.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]402
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]403 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
404 <tt>dynamic_cast&lt;&gt;</tt> or Java's <tt>instanceof</tt> operator, can be
405 abused. In particular, you should not use big chained <tt>if/then/else</tt>
406 blocks to check for lots of different variants of classes. If you find
407 yourself wanting to do this, it is much cleaner and more efficient to use the
408 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]409
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]410 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]411
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]412 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
413
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]414 <dd><p>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]415 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as an
416 argument (which it then propagates). This can sometimes be useful, allowing
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]417 you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]418
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]419 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]420
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]421 <dd><p>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]422 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
423 as an argument (which it then propagates). This can sometimes be useful,
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]424 allowing you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]425
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]426</dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]427
428<p>These five templates can be used with any classes, whether they have a
429v-table or not. To add support for these templates, you simply need to add
430<tt>classof</tt> static methods to the class you are interested casting
431to. Describing this is currently outside the scope of this document, but there
432are lots of examples in the LLVM source base.</p>
433
434</div>
435
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]436
437<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]438<h3>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]439 <a name="string_apis">Passing strings (the <tt>StringRef</tt>
440and <tt>Twine</tt> classes)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]441</h3>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]442
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]443<div>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]444
445<p>Although LLVM generally does not do much string manipulation, we do have
Chris Lattner81187ae2009-07-25 07:16:59 +0000[diff] [blame]446several important APIs which take strings. Two important examples are the
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]447Value class -- which has names for instructions, functions, etc. -- and the
448StringMap class which is used extensively in LLVM and Clang.</p>
449
450<p>These are generic classes, and they need to be able to accept strings which
451may have embedded null characters. Therefore, they cannot simply take
Chris Lattner81187ae2009-07-25 07:16:59 +0000[diff] [blame]452a <tt>const char *</tt>, and taking a <tt>const std::string&amp;</tt> requires
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]453clients to perform a heap allocation which is usually unnecessary. Instead,
Benjamin Kramer38e59892010-07-14 22:38:02 +0000[diff] [blame]454many LLVM APIs use a <tt>StringRef</tt> or a <tt>const Twine&amp;</tt> for
455passing strings efficiently.</p>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]456
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]457<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]458<h4>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]459 <a name="StringRef">The <tt>StringRef</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]460</h4>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]461
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]462<div>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]463
464<p>The <tt>StringRef</tt> data type represents a reference to a constant string
465(a character array and a length) and supports the common operations available
466on <tt>std:string</tt>, but does not require heap allocation.</p>
467
Chris Lattner81187ae2009-07-25 07:16:59 +0000[diff] [blame]468<p>It can be implicitly constructed using a C style null-terminated string,
469an <tt>std::string</tt>, or explicitly with a character pointer and length.
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]470For example, the <tt>StringRef</tt> find function is declared as:</p>
Chris Lattner81187ae2009-07-25 07:16:59 +0000[diff] [blame]471
Benjamin Kramer38e59892010-07-14 22:38:02 +0000[diff] [blame]472<pre class="doc_code">
473 iterator find(StringRef Key);
474</pre>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]475
476<p>and clients can call it using any one of:</p>
477
Benjamin Kramer38e59892010-07-14 22:38:02 +0000[diff] [blame]478<pre class="doc_code">
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]479 Map.find("foo"); <i>// Lookup "foo"</i>
480 Map.find(std::string("bar")); <i>// Lookup "bar"</i>
481 Map.find(StringRef("\0baz", 4)); <i>// Lookup "\0baz"</i>
482</pre>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]483
484<p>Similarly, APIs which need to return a string may return a <tt>StringRef</tt>
485instance, which can be used directly or converted to an <tt>std::string</tt>
486using the <tt>str</tt> member function. See
487"<tt><a href="/doxygen/classllvm_1_1StringRef_8h-source.html">llvm/ADT/StringRef.h</a></tt>"
488for more information.</p>
489
490<p>You should rarely use the <tt>StringRef</tt> class directly, because it contains
491pointers to external memory it is not generally safe to store an instance of the
Benjamin Kramer38e59892010-07-14 22:38:02 +0000[diff] [blame]492class (unless you know that the external storage will not be freed). StringRef is
493small and pervasive enough in LLVM that it should always be passed by value.</p>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]494
495</div>
496
497<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]498<h4>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]499 <a name="Twine">The <tt>Twine</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]500</h4>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]501
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]502<div>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]503
504<p>The <tt>Twine</tt> class is an efficient way for APIs to accept concatenated
505strings. For example, a common LLVM paradigm is to name one instruction based on
506the name of another instruction with a suffix, for example:</p>
507
508<div class="doc_code">
509<pre>
510 New = CmpInst::Create(<i>...</i>, SO->getName() + ".cmp");
511</pre>
512</div>
513
514<p>The <tt>Twine</tt> class is effectively a
515lightweight <a href="http://en.wikipedia.org/wiki/Rope_(computer_science)">rope</a>
516which points to temporary (stack allocated) objects. Twines can be implicitly
517constructed as the result of the plus operator applied to strings (i.e., a C
518strings, an <tt>std::string</tt>, or a <tt>StringRef</tt>). The twine delays the
Dan Gohmancf0c9bc2010-02-25 23:51:27 +0000[diff] [blame]519actual concatenation of strings until it is actually required, at which point
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]520it can be efficiently rendered directly into a character array. This avoids
521unnecessary heap allocation involved in constructing the temporary results of
522string concatenation. See
523"<tt><a href="/doxygen/classllvm_1_1Twine_8h-source.html">llvm/ADT/Twine.h</a></tt>"
Benjamin Kramere15192b2009-08-05 15:42:44 +0000[diff] [blame]524for more information.</p>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]525
526<p>As with a <tt>StringRef</tt>, <tt>Twine</tt> objects point to external memory
527and should almost never be stored or mentioned directly. They are intended
528solely for use when defining a function which should be able to efficiently
529accept concatenated strings.</p>
530
531</div>
532
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]533</div>
Daniel Dunbar6e0d1cb2009-07-25 04:41:11 +0000[diff] [blame]534
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]535<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]536<h3>
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]537 <a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]538</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]539
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]540<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]541
542<p>Often when working on your pass you will put a bunch of debugging printouts
543and other code into your pass. After you get it working, you want to remove
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]544it, but you may need it again in the future (to work out new bugs that you run
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]545across).</p>
546
547<p> Naturally, because of this, you don't want to delete the debug printouts,
548but you don't want them to always be noisy. A standard compromise is to comment
549them out, allowing you to enable them if you need them in the future.</p>
550
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]551<p>The "<tt><a href="/doxygen/Debug_8h-source.html">llvm/Support/Debug.h</a></tt>"
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]552file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
553this problem. Basically, you can put arbitrary code into the argument of the
554<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
555tool) is run with the '<tt>-debug</tt>' command line argument:</p>
556
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]557<div class="doc_code">
558<pre>
Daniel Dunbar06388ae2009-07-25 01:55:32 +0000[diff] [blame]559DEBUG(errs() &lt;&lt; "I am here!\n");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]560</pre>
561</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]562
563<p>Then you can run your pass like this:</p>
564
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]565<div class="doc_code">
566<pre>
567$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]568<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]569$ opt &lt; a.bc &gt; /dev/null -mypass -debug
570I am here!
571</pre>
572</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]573
574<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
575to not have to create "yet another" command line option for the debug output for
576your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
577so they do not cause a performance impact at all (for the same reason, they
578should also not contain side-effects!).</p>
579
580<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
581enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
582"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
583program hasn't been started yet, you can always just run it with
584<tt>-debug</tt>.</p>
585
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]586<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]587<h4>
Chris Lattnerc9151082005-04-26 22:57:07 +0000[diff] [blame]588 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]589 the <tt>-debug-only</tt> option</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]590</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]591
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]592<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]593
594<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
595just turns on <b>too much</b> information (such as when working on the code
596generator). If you want to enable debug information with more fine-grained
597control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
598option as follows:</p>
599
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]600<div class="doc_code">
601<pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]602#undef DEBUG_TYPE
Daniel Dunbar06388ae2009-07-25 01:55:32 +0000[diff] [blame]603DEBUG(errs() &lt;&lt; "No debug type\n");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]604#define DEBUG_TYPE "foo"
Daniel Dunbar06388ae2009-07-25 01:55:32 +0000[diff] [blame]605DEBUG(errs() &lt;&lt; "'foo' debug type\n");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]606#undef DEBUG_TYPE
607#define DEBUG_TYPE "bar"
Daniel Dunbar06388ae2009-07-25 01:55:32 +0000[diff] [blame]608DEBUG(errs() &lt;&lt; "'bar' debug type\n"));
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]609#undef DEBUG_TYPE
610#define DEBUG_TYPE ""
Daniel Dunbar06388ae2009-07-25 01:55:32 +0000[diff] [blame]611DEBUG(errs() &lt;&lt; "No debug type (2)\n");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]612</pre>
613</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]614
615<p>Then you can run your pass like this:</p>
616
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]617<div class="doc_code">
618<pre>
619$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]620<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]621$ opt &lt; a.bc &gt; /dev/null -mypass -debug
622No debug type
623'foo' debug type
624'bar' debug type
625No debug type (2)
626$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo
627'foo' debug type
628$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar
629'bar' debug type
630</pre>
631</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]632
633<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
634a file, to specify the debug type for the entire module (if you do this before
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]635you <tt>#include "llvm/Support/Debug.h"</tt>, you don't have to insert the ugly
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]636<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
637"bar", because there is no system in place to ensure that names do not
638conflict. If two different modules use the same string, they will all be turned
639on when the name is specified. This allows, for example, all debug information
640for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]641even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]642
Daniel Dunbarc3c92392009-08-07 23:48:59 +0000[diff] [blame]643<p>The <tt>DEBUG_WITH_TYPE</tt> macro is also available for situations where you
644would like to set <tt>DEBUG_TYPE</tt>, but only for one specific <tt>DEBUG</tt>
645statement. It takes an additional first parameter, which is the type to use. For
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]646example, the preceding example could be written as:</p>
Daniel Dunbarc3c92392009-08-07 23:48:59 +0000[diff] [blame]647
648
649<div class="doc_code">
650<pre>
651DEBUG_WITH_TYPE("", errs() &lt;&lt; "No debug type\n");
652DEBUG_WITH_TYPE("foo", errs() &lt;&lt; "'foo' debug type\n");
653DEBUG_WITH_TYPE("bar", errs() &lt;&lt; "'bar' debug type\n"));
654DEBUG_WITH_TYPE("", errs() &lt;&lt; "No debug type (2)\n");
655</pre>
656</div>
657
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]658</div>
659
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]660</div>
661
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]662<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]663<h3>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]664 <a name="Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]665 option</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]666</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]667
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]668<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]669
670<p>The "<tt><a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]671href="/doxygen/Statistic_8h-source.html">llvm/ADT/Statistic.h</a></tt>" file
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]672provides a class named <tt>Statistic</tt> that is used as a unified way to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]673keep track of what the LLVM compiler is doing and how effective various
674optimizations are. It is useful to see what optimizations are contributing to
675making a particular program run faster.</p>
676
677<p>Often you may run your pass on some big program, and you're interested to see
678how many times it makes a certain transformation. Although you can do this with
679hand inspection, or some ad-hoc method, this is a real pain and not very useful
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]680for big programs. Using the <tt>Statistic</tt> class makes it very easy to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]681keep track of this information, and the calculated information is presented in a
682uniform manner with the rest of the passes being executed.</p>
683
684<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
685it are as follows:</p>
686
687<ol>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]688 <li><p>Define your statistic like this:</p>
689
690<div class="doc_code">
691<pre>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]692#define <a href="#DEBUG_TYPE">DEBUG_TYPE</a> "mypassname" <i>// This goes before any #includes.</i>
693STATISTIC(NumXForms, "The # of times I did stuff");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]694</pre>
695</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]696
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]697 <p>The <tt>STATISTIC</tt> macro defines a static variable, whose name is
698 specified by the first argument. The pass name is taken from the DEBUG_TYPE
699 macro, and the description is taken from the second argument. The variable
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]700 defined ("NumXForms" in this case) acts like an unsigned integer.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]701
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]702 <li><p>Whenever you make a transformation, bump the counter:</p>
703
704<div class="doc_code">
705<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]706++NumXForms; // <i>I did stuff!</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]707</pre>
708</div>
709
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]710 </li>
711 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]712
713 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
714 statistics gathered, use the '<tt>-stats</tt>' option:</p>
715
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]716<div class="doc_code">
717<pre>
718$ opt -stats -mypassname &lt; program.bc &gt; /dev/null
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]719<i>... statistics output ...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]720</pre>
721</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]722
Reid Spencer6b6c73e2007-02-09 16:00:28 +0000[diff] [blame]723 <p> When running <tt>opt</tt> on a C file from the SPEC benchmark
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]724suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]725
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]726<div class="doc_code">
727<pre>
Gabor Greif04367bf2007-07-06 22:07:22 +0000[diff] [blame]728 7646 bitcodewriter - Number of normal instructions
729 725 bitcodewriter - Number of oversized instructions
730 129996 bitcodewriter - Number of bitcode bytes written
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]731 2817 raise - Number of insts DCEd or constprop'd
732 3213 raise - Number of cast-of-self removed
733 5046 raise - Number of expression trees converted
734 75 raise - Number of other getelementptr's formed
735 138 raise - Number of load/store peepholes
736 42 deadtypeelim - Number of unused typenames removed from symtab
737 392 funcresolve - Number of varargs functions resolved
738 27 globaldce - Number of global variables removed
739 2 adce - Number of basic blocks removed
740 134 cee - Number of branches revectored
741 49 cee - Number of setcc instruction eliminated
742 532 gcse - Number of loads removed
743 2919 gcse - Number of instructions removed
744 86 indvars - Number of canonical indvars added
745 87 indvars - Number of aux indvars removed
746 25 instcombine - Number of dead inst eliminate
747 434 instcombine - Number of insts combined
748 248 licm - Number of load insts hoisted
749 1298 licm - Number of insts hoisted to a loop pre-header
750 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
751 75 mem2reg - Number of alloca's promoted
752 1444 cfgsimplify - Number of blocks simplified
753</pre>
754</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]755
756<p>Obviously, with so many optimizations, having a unified framework for this
757stuff is very nice. Making your pass fit well into the framework makes it more
758maintainable and useful.</p>
759
760</div>
761
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]762<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]763<h3>
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]764 <a name="ViewGraph">Viewing graphs while debugging code</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]765</h3>
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]766
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]767<div>
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]768
769<p>Several of the important data structures in LLVM are graphs: for example
770CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
771LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
772<a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
773DAGs</a>. In many cases, while debugging various parts of the compiler, it is
774nice to instantly visualize these graphs.</p>
775
776<p>LLVM provides several callbacks that are available in a debug build to do
777exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
778the current LLVM tool will pop up a window containing the CFG for the function
779where each basic block is a node in the graph, and each node contains the
780instructions in the block. Similarly, there also exists
781<tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
782<tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
783and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]784you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]785up a window. Alternatively, you can sprinkle calls to these functions in your
786code in places you want to debug.</p>
787
788<p>Getting this to work requires a small amount of configuration. On Unix
789systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
790toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
791Mac OS/X, download and install the Mac OS/X <a
792href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]793<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or wherever you install
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]794it) to your path. Once in your system and path are set up, rerun the LLVM
795configure script and rebuild LLVM to enable this functionality.</p>
796
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]797<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
798<i>interesting</i> nodes in large complex graphs. From gdb, if you
799<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]800next <tt>call DAG.viewGraph()</tt> would highlight the node in the
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]801specified color (choices of colors can be found at <a
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]802href="http://www.graphviz.org/doc/info/colors.html">colors</a>.) More
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]803complex node attributes can be provided with <tt>call
804DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
805found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
806Attributes</a>.) If you want to restart and clear all the current graph
807attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
808
Chris Lattner83f94672011-06-13 15:59:35 +0000[diff] [blame]809<p>Note that graph visualization features are compiled out of Release builds
810to reduce file size. This means that you need a Debug+Asserts or
811Release+Asserts build to use these features.</p>
812
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]813</div>
814
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]815</div>
816
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]817<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]818<h2>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]819 <a name="datastructure">Picking the Right Data Structure for a Task</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]820</h2>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]821<!-- *********************************************************************** -->
822
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]823<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]824
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]825<p>LLVM has a plethora of data structures in the <tt>llvm/ADT/</tt> directory,
826 and we commonly use STL data structures. This section describes the trade-offs
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]827 you should consider when you pick one.</p>
828
829<p>
830The first step is a choose your own adventure: do you want a sequential
831container, a set-like container, or a map-like container? The most important
832thing when choosing a container is the algorithmic properties of how you plan to
833access the container. Based on that, you should use:</p>
834
835<ul>
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]836<li>a <a href="#ds_map">map-like</a> container if you need efficient look-up
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]837 of an value based on another value. Map-like containers also support
838 efficient queries for containment (whether a key is in the map). Map-like
839 containers generally do not support efficient reverse mapping (values to
840 keys). If you need that, use two maps. Some map-like containers also
841 support efficient iteration through the keys in sorted order. Map-like
842 containers are the most expensive sort, only use them if you need one of
843 these capabilities.</li>
844
845<li>a <a href="#ds_set">set-like</a> container if you need to put a bunch of
846 stuff into a container that automatically eliminates duplicates. Some
847 set-like containers support efficient iteration through the elements in
848 sorted order. Set-like containers are more expensive than sequential
849 containers.
850</li>
851
852<li>a <a href="#ds_sequential">sequential</a> container provides
853 the most efficient way to add elements and keeps track of the order they are
854 added to the collection. They permit duplicates and support efficient
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]855 iteration, but do not support efficient look-up based on a key.
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]856</li>
857
Chris Lattnerdced9fb2009-07-25 07:22:20 +0000[diff] [blame]858<li>a <a href="#ds_string">string</a> container is a specialized sequential
859 container or reference structure that is used for character or byte
860 arrays.</li>
861
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]862<li>a <a href="#ds_bit">bit</a> container provides an efficient way to store and
863 perform set operations on sets of numeric id's, while automatically
864 eliminating duplicates. Bit containers require a maximum of 1 bit for each
865 identifier you want to store.
866</li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]867</ul>
868
869<p>
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]870Once the proper category of container is determined, you can fine tune the
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]871memory use, constant factors, and cache behaviors of access by intelligently
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]872picking a member of the category. Note that constant factors and cache behavior
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]873can be a big deal. If you have a vector that usually only contains a few
874elements (but could contain many), for example, it's much better to use
875<a href="#dss_smallvector">SmallVector</a> than <a href="#dss_vector">vector</a>
876. Doing so avoids (relatively) expensive malloc/free calls, which dwarf the
877cost of adding the elements to the container. </p>
878
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]879<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]880<h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]881 <a name="ds_sequential">Sequential Containers (std::vector, std::list, etc)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]882</h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]883
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]884<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]885There are a variety of sequential containers available for you, based on your
886needs. Pick the first in this section that will do what you want.
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]887
888<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]889<h4>
Chris Lattner8ae42612011-04-05 23:18:20 +0000[diff] [blame]890 <a name="dss_arrayref">llvm/ADT/ArrayRef.h</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]891</h4>
Chris Lattner8ae42612011-04-05 23:18:20 +0000[diff] [blame]892
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]893<div>
Chris Lattner8ae42612011-04-05 23:18:20 +0000[diff] [blame]894<p>The llvm::ArrayRef class is the preferred class to use in an interface that
895 accepts a sequential list of elements in memory and just reads from them. By
896 taking an ArrayRef, the API can be passed a fixed size array, an std::vector,
897 an llvm::SmallVector and anything else that is contiguous in memory.
898</p>
899</div>
900
901
902
903<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]904<h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]905 <a name="dss_fixedarrays">Fixed Size Arrays</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]906</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]907
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]908<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]909<p>Fixed size arrays are very simple and very fast. They are good if you know
910exactly how many elements you have, or you have a (low) upper bound on how many
911you have.</p>
912</div>
913
914<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]915<h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]916 <a name="dss_heaparrays">Heap Allocated Arrays</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]917</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]918
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]919<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]920<p>Heap allocated arrays (new[] + delete[]) are also simple. They are good if
921the number of elements is variable, if you know how many elements you will need
922before the array is allocated, and if the array is usually large (if not,
923consider a <a href="#dss_smallvector">SmallVector</a>). The cost of a heap
924allocated array is the cost of the new/delete (aka malloc/free). Also note that
925if you are allocating an array of a type with a constructor, the constructor and
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]926destructors will be run for every element in the array (re-sizable vectors only
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]927construct those elements actually used).</p>
928</div>
929
930<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]931<h4>
Chris Lattner9d69d4a2011-07-18 01:40:02 +0000[diff] [blame]932 <a name="dss_tinyptrvector">"llvm/ADT/TinyPtrVector.h"</a>
933</h4>
934
935
936<div>
937<p><tt>TinyPtrVector&lt;Type&gt;</tt> is a highly specialized collection class
938that is optimized to avoid allocation in the case when a vector has zero or one
939elements. It has two major restrictions: 1) it can only hold values of pointer
940type, and 2) it cannot hold a null pointer.</p>
941
942<p>Since this container is highly specialized, it is rarely used.</p>
943
944</div>
945
946<div>
947
948<!-- _______________________________________________________________________ -->
949<h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]950 <a name="dss_smallvector">"llvm/ADT/SmallVector.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]951</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]952
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]953<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]954<p><tt>SmallVector&lt;Type, N&gt;</tt> is a simple class that looks and smells
955just like <tt>vector&lt;Type&gt;</tt>:
956it supports efficient iteration, lays out elements in memory order (so you can
957do pointer arithmetic between elements), supports efficient push_back/pop_back
958operations, supports efficient random access to its elements, etc.</p>
959
960<p>The advantage of SmallVector is that it allocates space for
961some number of elements (N) <b>in the object itself</b>. Because of this, if
962the SmallVector is dynamically smaller than N, no malloc is performed. This can
963be a big win in cases where the malloc/free call is far more expensive than the
964code that fiddles around with the elements.</p>
965
966<p>This is good for vectors that are "usually small" (e.g. the number of
967predecessors/successors of a block is usually less than 8). On the other hand,
968this makes the size of the SmallVector itself large, so you don't want to
969allocate lots of them (doing so will waste a lot of space). As such,
970SmallVectors are most useful when on the stack.</p>
971
972<p>SmallVector also provides a nice portable and efficient replacement for
973<tt>alloca</tt>.</p>
974
975</div>
976
977<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]978<h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]979 <a name="dss_vector">&lt;vector&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]980</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]981
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]982<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]983<p>
984std::vector is well loved and respected. It is useful when SmallVector isn't:
985when the size of the vector is often large (thus the small optimization will
986rarely be a benefit) or if you will be allocating many instances of the vector
987itself (which would waste space for elements that aren't in the container).
988vector is also useful when interfacing with code that expects vectors :).
989</p>
Chris Lattner32d84762007-02-05 06:30:51 +0000[diff] [blame]990
991<p>One worthwhile note about std::vector: avoid code like this:</p>
992
993<div class="doc_code">
994<pre>
995for ( ... ) {
Chris Lattner9bb3dbb2007-03-28 18:27:57 +0000[diff] [blame]996 std::vector&lt;foo&gt; V;
Chris Lattner32d84762007-02-05 06:30:51 +0000[diff] [blame]997 use V;
998}
999</pre>
1000</div>
1001
1002<p>Instead, write this as:</p>
1003
1004<div class="doc_code">
1005<pre>
Chris Lattner9bb3dbb2007-03-28 18:27:57 +0000[diff] [blame]1006std::vector&lt;foo&gt; V;
Chris Lattner32d84762007-02-05 06:30:51 +0000[diff] [blame]1007for ( ... ) {
1008 use V;
1009 V.clear();
1010}
1011</pre>
1012</div>
1013
1014<p>Doing so will save (at least) one heap allocation and free per iteration of
1015the loop.</p>
1016
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1017</div>
1018
1019<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1020<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1021 <a name="dss_deque">&lt;deque&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1022</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1023
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1024<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1025<p>std::deque is, in some senses, a generalized version of std::vector. Like
1026std::vector, it provides constant time random access and other similar
1027properties, but it also provides efficient access to the front of the list. It
1028does not guarantee continuity of elements within memory.</p>
1029
1030<p>In exchange for this extra flexibility, std::deque has significantly higher
1031constant factor costs than std::vector. If possible, use std::vector or
1032something cheaper.</p>
1033</div>
1034
1035<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1036<h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1037 <a name="dss_list">&lt;list&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1038</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1039
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1040<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1041<p>std::list is an extremely inefficient class that is rarely useful.
1042It performs a heap allocation for every element inserted into it, thus having an
1043extremely high constant factor, particularly for small data types. std::list
1044also only supports bidirectional iteration, not random access iteration.</p>
1045
1046<p>In exchange for this high cost, std::list supports efficient access to both
1047ends of the list (like std::deque, but unlike std::vector or SmallVector). In
1048addition, the iterator invalidation characteristics of std::list are stronger
1049than that of a vector class: inserting or removing an element into the list does
1050not invalidate iterator or pointers to other elements in the list.</p>
1051</div>
1052
1053<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1054<h4>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1055 <a name="dss_ilist">llvm/ADT/ilist.h</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1056</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1057
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1058<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1059<p><tt>ilist&lt;T&gt;</tt> implements an 'intrusive' doubly-linked list. It is
1060intrusive, because it requires the element to store and provide access to the
1061prev/next pointers for the list.</p>
1062
Gabor Greif2946d1c2009-02-27 12:02:19 +0000[diff] [blame]1063<p><tt>ilist</tt> has the same drawbacks as <tt>std::list</tt>, and additionally
1064requires an <tt>ilist_traits</tt> implementation for the element type, but it
1065provides some novel characteristics. In particular, it can efficiently store
1066polymorphic objects, the traits class is informed when an element is inserted or
Gabor Greif0cbcabe2009-03-12 09:47:03 +0000[diff] [blame]1067removed from the list, and <tt>ilist</tt>s are guaranteed to support a
1068constant-time splice operation.</p>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1069
Gabor Greif0cbcabe2009-03-12 09:47:03 +0000[diff] [blame]1070<p>These properties are exactly what we want for things like
1071<tt>Instruction</tt>s and basic blocks, which is why these are implemented with
1072<tt>ilist</tt>s.</p>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1073
1074Related classes of interest are explained in the following subsections:
1075 <ul>
Gabor Greif01862502009-02-27 13:28:07 +0000[diff] [blame]1076 <li><a href="#dss_ilist_traits">ilist_traits</a></li>
Gabor Greif2946d1c2009-02-27 12:02:19 +0000[diff] [blame]1077 <li><a href="#dss_iplist">iplist</a></li>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1078 <li><a href="#dss_ilist_node">llvm/ADT/ilist_node.h</a></li>
Gabor Greif6a65f422009-03-12 10:30:31 +0000[diff] [blame]1079 <li><a href="#dss_ilist_sentinel">Sentinels</a></li>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1080 </ul>
1081</div>
1082
1083<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1084<h4>
Argyrios Kyrtzidis81df0892011-06-15 19:56:01 +0000[diff] [blame]1085 <a name="dss_packedvector">llvm/ADT/PackedVector.h</a>
1086</h4>
1087
1088<div>
1089<p>
1090Useful for storing a vector of values using only a few number of bits for each
1091value. Apart from the standard operations of a vector-like container, it can
1092also perform an 'or' set operation.
1093</p>
1094
1095<p>For example:</p>
1096
1097<div class="doc_code">
1098<pre>
1099enum State {
1100 None = 0x0,
1101 FirstCondition = 0x1,
1102 SecondCondition = 0x2,
1103 Both = 0x3
1104};
1105
1106State get() {
1107 PackedVector&lt;State, 2&gt; Vec1;
1108 Vec1.push_back(FirstCondition);
1109
1110 PackedVector&lt;State, 2&gt; Vec2;
1111 Vec2.push_back(SecondCondition);
1112
1113 Vec1 |= Vec2;
1114 return Vec1[0]; // returns 'Both'.
1115}
1116</pre>
1117</div>
1118
1119</div>
1120
1121<!-- _______________________________________________________________________ -->
1122<h4>
Gabor Greif01862502009-02-27 13:28:07 +0000[diff] [blame]1123 <a name="dss_ilist_traits">ilist_traits</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1124</h4>
Gabor Greif01862502009-02-27 13:28:07 +0000[diff] [blame]1125
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1126<div>
Gabor Greif01862502009-02-27 13:28:07 +0000[diff] [blame]1127<p><tt>ilist_traits&lt;T&gt;</tt> is <tt>ilist&lt;T&gt;</tt>'s customization
1128mechanism. <tt>iplist&lt;T&gt;</tt> (and consequently <tt>ilist&lt;T&gt;</tt>)
1129publicly derive from this traits class.</p>
1130</div>
1131
1132<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1133<h4>
Gabor Greif2946d1c2009-02-27 12:02:19 +0000[diff] [blame]1134 <a name="dss_iplist">iplist</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1135</h4>
Gabor Greif2946d1c2009-02-27 12:02:19 +0000[diff] [blame]1136
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1137<div>
Gabor Greif2946d1c2009-02-27 12:02:19 +0000[diff] [blame]1138<p><tt>iplist&lt;T&gt;</tt> is <tt>ilist&lt;T&gt;</tt>'s base and as such
Gabor Greif0cbcabe2009-03-12 09:47:03 +0000[diff] [blame]1139supports a slightly narrower interface. Notably, inserters from
1140<tt>T&amp;</tt> are absent.</p>
Gabor Greif01862502009-02-27 13:28:07 +0000[diff] [blame]1141
1142<p><tt>ilist_traits&lt;T&gt;</tt> is a public base of this class and can be
1143used for a wide variety of customizations.</p>
Gabor Greif2946d1c2009-02-27 12:02:19 +0000[diff] [blame]1144</div>
1145
1146<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1147<h4>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1148 <a name="dss_ilist_node">llvm/ADT/ilist_node.h</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1149</h4>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1150
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1151<div>
Gabor Greif3899e492009-02-27 11:37:41 +0000[diff] [blame]1152<p><tt>ilist_node&lt;T&gt;</tt> implements a the forward and backward links
1153that are expected by the <tt>ilist&lt;T&gt;</tt> (and analogous containers)
1154in the default manner.</p>
1155
1156<p><tt>ilist_node&lt;T&gt;</tt>s are meant to be embedded in the node type
Gabor Greif0cbcabe2009-03-12 09:47:03 +0000[diff] [blame]1157<tt>T</tt>, usually <tt>T</tt> publicly derives from
1158<tt>ilist_node&lt;T&gt;</tt>.</p>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1159</div>
1160
1161<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1162<h4>
Gabor Greif6a65f422009-03-12 10:30:31 +0000[diff] [blame]1163 <a name="dss_ilist_sentinel">Sentinels</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1164</h4>
Gabor Greif6a65f422009-03-12 10:30:31 +0000[diff] [blame]1165
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1166<div>
Dan Gohmancf0c9bc2010-02-25 23:51:27 +0000[diff] [blame]1167<p><tt>ilist</tt>s have another specialty that must be considered. To be a good
Gabor Greif6a65f422009-03-12 10:30:31 +0000[diff] [blame]1168citizen in the C++ ecosystem, it needs to support the standard container
1169operations, such as <tt>begin</tt> and <tt>end</tt> iterators, etc. Also, the
1170<tt>operator--</tt> must work correctly on the <tt>end</tt> iterator in the
1171case of non-empty <tt>ilist</tt>s.</p>
1172
1173<p>The only sensible solution to this problem is to allocate a so-called
1174<i>sentinel</i> along with the intrusive list, which serves as the <tt>end</tt>
1175iterator, providing the back-link to the last element. However conforming to the
1176C++ convention it is illegal to <tt>operator++</tt> beyond the sentinel and it
1177also must not be dereferenced.</p>
1178
1179<p>These constraints allow for some implementation freedom to the <tt>ilist</tt>
1180how to allocate and store the sentinel. The corresponding policy is dictated
1181by <tt>ilist_traits&lt;T&gt;</tt>. By default a <tt>T</tt> gets heap-allocated
1182whenever the need for a sentinel arises.</p>
1183
1184<p>While the default policy is sufficient in most cases, it may break down when
1185<tt>T</tt> does not provide a default constructor. Also, in the case of many
1186instances of <tt>ilist</tt>s, the memory overhead of the associated sentinels
1187is wasted. To alleviate the situation with numerous and voluminous
1188<tt>T</tt>-sentinels, sometimes a trick is employed, leading to <i>ghostly
1189sentinels</i>.</p>
1190
1191<p>Ghostly sentinels are obtained by specially-crafted <tt>ilist_traits&lt;T&gt;</tt>
1192which superpose the sentinel with the <tt>ilist</tt> instance in memory. Pointer
1193arithmetic is used to obtain the sentinel, which is relative to the
1194<tt>ilist</tt>'s <tt>this</tt> pointer. The <tt>ilist</tt> is augmented by an
1195extra pointer, which serves as the back-link of the sentinel. This is the only
1196field in the ghostly sentinel which can be legally accessed.</p>
1197</div>
1198
1199<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1200<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1201 <a name="dss_other">Other Sequential Container options</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1202</h4>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1203
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1204<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1205<p>Other STL containers are available, such as std::string.</p>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1206
1207<p>There are also various STL adapter classes such as std::queue,
1208std::priority_queue, std::stack, etc. These provide simplified access to an
1209underlying container but don't affect the cost of the container itself.</p>
1210
1211</div>
1212
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1213</div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1214
1215<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1216<h3>
Chris Lattner7314a202011-07-22 20:46:49 +0000[diff] [blame]1217 <a name="ds_string">String-like containers</a>
1218</h3>
1219
1220<div>
1221
1222<p>
1223TODO: const char* vs stringref vs smallstring vs std::string. Describe twine,
1224xref to #string_apis.
1225</p>
1226
1227</div>
1228
1229
1230<!-- ======================================================================= -->
1231<h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1232 <a name="ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1233</h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1234
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1235<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1236
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1237<p>Set-like containers are useful when you need to canonicalize multiple values
1238into a single representation. There are several different choices for how to do
1239this, providing various trade-offs.</p>
1240
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1241<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1242<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1243 <a name="dss_sortedvectorset">A sorted 'vector'</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1244</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1245
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1246<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1247
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame]1248<p>If you intend to insert a lot of elements, then do a lot of queries, a
1249great approach is to use a vector (or other sequential container) with
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1250std::sort+std::unique to remove duplicates. This approach works really well if
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame]1251your usage pattern has these two distinct phases (insert then query), and can be
1252coupled with a good choice of <a href="#ds_sequential">sequential container</a>.
1253</p>
1254
1255<p>
1256This combination provides the several nice properties: the result data is
1257contiguous in memory (good for cache locality), has few allocations, is easy to
1258address (iterators in the final vector are just indices or pointers), and can be
1259efficiently queried with a standard binary or radix search.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1260
1261</div>
1262
1263<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1264<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1265 <a name="dss_smallset">"llvm/ADT/SmallSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1266</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1267
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1268<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1269
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1270<p>If you have a set-like data structure that is usually small and whose elements
Chris Lattner4ddfac12007-02-03 07:59:51 +0000[diff] [blame]1271are reasonably small, a <tt>SmallSet&lt;Type, N&gt;</tt> is a good choice. This set
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1272has space for N elements in place (thus, if the set is dynamically smaller than
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1273N, no malloc traffic is required) and accesses them with a simple linear search.
1274When the set grows beyond 'N' elements, it allocates a more expensive representation that
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1275guarantees efficient access (for most types, it falls back to std::set, but for
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1276pointers it uses something far better, <a
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1277href="#dss_smallptrset">SmallPtrSet</a>).</p>
1278
1279<p>The magic of this class is that it handles small sets extremely efficiently,
1280but gracefully handles extremely large sets without loss of efficiency. The
1281drawback is that the interface is quite small: it supports insertion, queries
1282and erasing, but does not support iteration.</p>
1283
1284</div>
1285
1286<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1287<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1288 <a name="dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1289</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1290
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1291<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1292
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]1293<p>SmallPtrSet has all the advantages of <tt>SmallSet</tt> (and a <tt>SmallSet</tt> of pointers is
1294transparently implemented with a <tt>SmallPtrSet</tt>), but also supports iterators. If
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1295more than 'N' insertions are performed, a single quadratically
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1296probed hash table is allocated and grows as needed, providing extremely
1297efficient access (constant time insertion/deleting/queries with low constant
1298factors) and is very stingy with malloc traffic.</p>
1299
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]1300<p>Note that, unlike <tt>std::set</tt>, the iterators of <tt>SmallPtrSet</tt> are invalidated
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1301whenever an insertion occurs. Also, the values visited by the iterators are not
1302visited in sorted order.</p>
1303
1304</div>
1305
1306<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1307<h4>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]1308 <a name="dss_denseset">"llvm/ADT/DenseSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1309</h4>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]1310
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1311<div>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]1312
1313<p>
1314DenseSet is a simple quadratically probed hash table. It excels at supporting
1315small values: it uses a single allocation to hold all of the pairs that
1316are currently inserted in the set. DenseSet is a great way to unique small
1317values that are not simple pointers (use <a
1318href="#dss_smallptrset">SmallPtrSet</a> for pointers). Note that DenseSet has
1319the same requirements for the value type that <a
1320href="#dss_densemap">DenseMap</a> has.
1321</p>
1322
1323</div>
1324
1325<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1326<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1327 <a name="dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1328</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1329
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1330<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1331
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1332<p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1333FoldingSet is an aggregate class that is really good at uniquing
1334expensive-to-create or polymorphic objects. It is a combination of a chained
1335hash table with intrusive links (uniqued objects are required to inherit from
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1336FoldingSetNode) that uses <a href="#dss_smallvector">SmallVector</a> as part of
1337its ID process.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1338
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1339<p>Consider a case where you want to implement a "getOrCreateFoo" method for
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1340a complex object (for example, a node in the code generator). The client has a
1341description of *what* it wants to generate (it knows the opcode and all the
1342operands), but we don't want to 'new' a node, then try inserting it into a set
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1343only to find out it already exists, at which point we would have to delete it
1344and return the node that already exists.
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1345</p>
1346
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1347<p>To support this style of client, FoldingSet perform a query with a
1348FoldingSetNodeID (which wraps SmallVector) that can be used to describe the
1349element that we want to query for. The query either returns the element
1350matching the ID or it returns an opaque ID that indicates where insertion should
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1351take place. Construction of the ID usually does not require heap traffic.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1352
1353<p>Because FoldingSet uses intrusive links, it can support polymorphic objects
1354in the set (for example, you can have SDNode instances mixed with LoadSDNodes).
1355Because the elements are individually allocated, pointers to the elements are
1356stable: inserting or removing elements does not invalidate any pointers to other
1357elements.
1358</p>
1359
1360</div>
1361
1362<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1363<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1364 <a name="dss_set">&lt;set&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1365</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1366
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1367<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1368
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1369<p><tt>std::set</tt> is a reasonable all-around set class, which is decent at
1370many things but great at nothing. std::set allocates memory for each element
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1371inserted (thus it is very malloc intensive) and typically stores three pointers
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1372per element in the set (thus adding a large amount of per-element space
1373overhead). It offers guaranteed log(n) performance, which is not particularly
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1374fast from a complexity standpoint (particularly if the elements of the set are
1375expensive to compare, like strings), and has extremely high constant factors for
1376lookup, insertion and removal.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1377
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1378<p>The advantages of std::set are that its iterators are stable (deleting or
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1379inserting an element from the set does not affect iterators or pointers to other
1380elements) and that iteration over the set is guaranteed to be in sorted order.
1381If the elements in the set are large, then the relative overhead of the pointers
1382and malloc traffic is not a big deal, but if the elements of the set are small,
1383std::set is almost never a good choice.</p>
1384
1385</div>
1386
1387<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1388<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1389 <a name="dss_setvector">"llvm/ADT/SetVector.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1390</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1391
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1392<div>
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1393<p>LLVM's SetVector&lt;Type&gt; is an adapter class that combines your choice of
1394a set-like container along with a <a href="#ds_sequential">Sequential
1395Container</a>. The important property
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1396that this provides is efficient insertion with uniquing (duplicate elements are
1397ignored) with iteration support. It implements this by inserting elements into
1398both a set-like container and the sequential container, using the set-like
1399container for uniquing and the sequential container for iteration.
1400</p>
1401
1402<p>The difference between SetVector and other sets is that the order of
1403iteration is guaranteed to match the order of insertion into the SetVector.
1404This property is really important for things like sets of pointers. Because
1405pointer values are non-deterministic (e.g. vary across runs of the program on
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1406different machines), iterating over the pointers in the set will
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1407not be in a well-defined order.</p>
1408
1409<p>
1410The drawback of SetVector is that it requires twice as much space as a normal
1411set and has the sum of constant factors from the set-like container and the
1412sequential container that it uses. Use it *only* if you need to iterate over
1413the elements in a deterministic order. SetVector is also expensive to delete
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1414elements out of (linear time), unless you use it's "pop_back" method, which is
1415faster.
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1416</p>
1417
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1418<p>SetVector is an adapter class that defaults to using std::vector and std::set
1419for the underlying containers, so it is quite expensive. However,
1420<tt>"llvm/ADT/SetVector.h"</tt> also provides a SmallSetVector class, which
1421defaults to using a SmallVector and SmallSet of a specified size. If you use
1422this, and if your sets are dynamically smaller than N, you will save a lot of
1423heap traffic.</p>
1424
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1425</div>
1426
1427<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1428<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1429 <a name="dss_uniquevector">"llvm/ADT/UniqueVector.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1430</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1431
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1432<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1433
1434<p>
1435UniqueVector is similar to <a href="#dss_setvector">SetVector</a>, but it
1436retains a unique ID for each element inserted into the set. It internally
1437contains a map and a vector, and it assigns a unique ID for each value inserted
1438into the set.</p>
1439
1440<p>UniqueVector is very expensive: its cost is the sum of the cost of
1441maintaining both the map and vector, it has high complexity, high constant
1442factors, and produces a lot of malloc traffic. It should be avoided.</p>
1443
1444</div>
1445
1446
1447<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1448<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1449 <a name="dss_otherset">Other Set-Like Container Options</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1450</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1451
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1452<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1453
1454<p>
1455The STL provides several other options, such as std::multiset and the various
Chris Lattnerf1a30822009-03-09 05:20:45 +0000[diff] [blame]1456"hash_set" like containers (whether from C++ TR1 or from the SGI library). We
1457never use hash_set and unordered_set because they are generally very expensive
1458(each insertion requires a malloc) and very non-portable.
1459</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1460
1461<p>std::multiset is useful if you're not interested in elimination of
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1462duplicates, but has all the drawbacks of std::set. A sorted vector (where you
1463don't delete duplicate entries) or some other approach is almost always
1464better.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1465
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1466</div>
1467
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1468</div>
1469
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1470<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1471<h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1472 <a name="ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1473</h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1474
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1475<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1476Map-like containers are useful when you want to associate data to a key. As
1477usual, there are a lot of different ways to do this. :)
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1478
1479<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1480<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1481 <a name="dss_sortedvectormap">A sorted 'vector'</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1482</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1483
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1484<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1485
1486<p>
1487If your usage pattern follows a strict insert-then-query approach, you can
1488trivially use the same approach as <a href="#dss_sortedvectorset">sorted vectors
1489for set-like containers</a>. The only difference is that your query function
1490(which uses std::lower_bound to get efficient log(n) lookup) should only compare
1491the key, not both the key and value. This yields the same advantages as sorted
1492vectors for sets.
1493</p>
1494</div>
1495
1496<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1497<h4>
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1498 <a name="dss_stringmap">"llvm/ADT/StringMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1499</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1500
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1501<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1502
1503<p>
1504Strings are commonly used as keys in maps, and they are difficult to support
1505efficiently: they are variable length, inefficient to hash and compare when
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1506long, expensive to copy, etc. StringMap is a specialized container designed to
1507cope with these issues. It supports mapping an arbitrary range of bytes to an
1508arbitrary other object.</p>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1509
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1510<p>The StringMap implementation uses a quadratically-probed hash table, where
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1511the buckets store a pointer to the heap allocated entries (and some other
1512stuff). The entries in the map must be heap allocated because the strings are
1513variable length. The string data (key) and the element object (value) are
1514stored in the same allocation with the string data immediately after the element
1515object. This container guarantees the "<tt>(char*)(&amp;Value+1)</tt>" points
1516to the key string for a value.</p>
1517
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1518<p>The StringMap is very fast for several reasons: quadratic probing is very
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1519cache efficient for lookups, the hash value of strings in buckets is not
Nick Lewycky2a80aca2010-08-01 23:18:45 +0000[diff] [blame]1520recomputed when looking up an element, StringMap rarely has to touch the
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1521memory for unrelated objects when looking up a value (even when hash collisions
1522happen), hash table growth does not recompute the hash values for strings
1523already in the table, and each pair in the map is store in a single allocation
1524(the string data is stored in the same allocation as the Value of a pair).</p>
1525
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1526<p>StringMap also provides query methods that take byte ranges, so it only ever
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1527copies a string if a value is inserted into the table.</p>
1528</div>
1529
1530<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1531<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1532 <a name="dss_indexedmap">"llvm/ADT/IndexedMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1533</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1534
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1535<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1536<p>
1537IndexedMap is a specialized container for mapping small dense integers (or
1538values that can be mapped to small dense integers) to some other type. It is
1539internally implemented as a vector with a mapping function that maps the keys to
1540the dense integer range.
1541</p>
1542
1543<p>
1544This is useful for cases like virtual registers in the LLVM code generator: they
1545have a dense mapping that is offset by a compile-time constant (the first
1546virtual register ID).</p>
1547
1548</div>
1549
1550<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1551<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1552 <a name="dss_densemap">"llvm/ADT/DenseMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1553</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1554
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1555<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1556
1557<p>
1558DenseMap is a simple quadratically probed hash table. It excels at supporting
1559small keys and values: it uses a single allocation to hold all of the pairs that
1560are currently inserted in the map. DenseMap is a great way to map pointers to
1561pointers, or map other small types to each other.
1562</p>
1563
1564<p>
1565There are several aspects of DenseMap that you should be aware of, however. The
1566iterators in a densemap are invalidated whenever an insertion occurs, unlike
1567map. Also, because DenseMap allocates space for a large number of key/value
Chris Lattnera4a264d2007-02-03 20:17:53 +0000[diff] [blame]1568pairs (it starts with 64 by default), it will waste a lot of space if your keys
1569or values are large. Finally, you must implement a partial specialization of
Chris Lattner76c1b972007-09-17 18:34:04 +0000[diff] [blame]1570DenseMapInfo for the key that you want, if it isn't already supported. This
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1571is required to tell DenseMap about two special marker values (which can never be
Chris Lattnera4a264d2007-02-03 20:17:53 +0000[diff] [blame]1572inserted into the map) that it needs internally.</p>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1573
1574</div>
1575
1576<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1577<h4>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]1578 <a name="dss_valuemap">"llvm/ADT/ValueMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1579</h4>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]1580
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1581<div>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]1582
1583<p>
1584ValueMap is a wrapper around a <a href="#dss_densemap">DenseMap</a> mapping
1585Value*s (or subclasses) to another type. When a Value is deleted or RAUW'ed,
1586ValueMap will update itself so the new version of the key is mapped to the same
1587value, just as if the key were a WeakVH. You can configure exactly how this
1588happens, and what else happens on these two events, by passing
1589a <code>Config</code> parameter to the ValueMap template.</p>
1590
1591</div>
1592
1593<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1594<h4>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]1595 <a name="dss_intervalmap">"llvm/ADT/IntervalMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1596</h4>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]1597
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1598<div>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]1599
1600<p> IntervalMap is a compact map for small keys and values. It maps key
1601intervals instead of single keys, and it will automatically coalesce adjacent
1602intervals. When then map only contains a few intervals, they are stored in the
1603map object itself to avoid allocations.</p>
1604
1605<p> The IntervalMap iterators are quite big, so they should not be passed around
1606as STL iterators. The heavyweight iterators allow a smaller data structure.</p>
1607
1608</div>
1609
1610<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1611<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1612 <a name="dss_map">&lt;map&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1613</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1614
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1615<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1616
1617<p>
1618std::map has similar characteristics to <a href="#dss_set">std::set</a>: it uses
1619a single allocation per pair inserted into the map, it offers log(n) lookup with
1620an extremely large constant factor, imposes a space penalty of 3 pointers per
1621pair in the map, etc.</p>
1622
1623<p>std::map is most useful when your keys or values are very large, if you need
1624to iterate over the collection in sorted order, or if you need stable iterators
1625into the map (i.e. they don't get invalidated if an insertion or deletion of
1626another element takes place).</p>
1627
1628</div>
1629
1630<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1631<h4>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]1632 <a name="dss_inteqclasses">"llvm/ADT/IntEqClasses.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1633</h4>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]1634
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1635<div>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]1636
1637<p>IntEqClasses provides a compact representation of equivalence classes of
1638small integers. Initially, each integer in the range 0..n-1 has its own
1639equivalence class. Classes can be joined by passing two class representatives to
1640the join(a, b) method. Two integers are in the same class when findLeader()
1641returns the same representative.</p>
1642
1643<p>Once all equivalence classes are formed, the map can be compressed so each
1644integer 0..n-1 maps to an equivalence class number in the range 0..m-1, where m
1645is the total number of equivalence classes. The map must be uncompressed before
1646it can be edited again.</p>
1647
1648</div>
1649
1650<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1651<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1652 <a name="dss_othermap">Other Map-Like Container Options</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1653</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1654
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1655<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1656
1657<p>
1658The STL provides several other options, such as std::multimap and the various
Chris Lattnerf1a30822009-03-09 05:20:45 +0000[diff] [blame]1659"hash_map" like containers (whether from C++ TR1 or from the SGI library). We
1660never use hash_set and unordered_set because they are generally very expensive
1661(each insertion requires a malloc) and very non-portable.</p>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1662
1663<p>std::multimap is useful if you want to map a key to multiple values, but has
1664all the drawbacks of std::map. A sorted vector or some other approach is almost
1665always better.</p>
1666
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1667</div>
1668
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1669</div>
1670
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1671<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1672<h3>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1673 <a name="ds_bit">Bit storage containers (BitVector, SparseBitVector)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1674</h3>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1675
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1676<div>
Chris Lattner7086ce72007-09-25 22:37:50 +0000[diff] [blame]1677<p>Unlike the other containers, there are only two bit storage containers, and
1678choosing when to use each is relatively straightforward.</p>
1679
1680<p>One additional option is
1681<tt>std::vector&lt;bool&gt;</tt>: we discourage its use for two reasons 1) the
1682implementation in many common compilers (e.g. commonly available versions of
1683GCC) is extremely inefficient and 2) the C++ standards committee is likely to
1684deprecate this container and/or change it significantly somehow. In any case,
1685please don't use it.</p>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1686
1687<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1688<h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1689 <a name="dss_bitvector">BitVector</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1690</h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1691
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1692<div>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1693<p> The BitVector container provides a dynamic size set of bits for manipulation.
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1694It supports individual bit setting/testing, as well as set operations. The set
1695operations take time O(size of bitvector), but operations are performed one word
1696at a time, instead of one bit at a time. This makes the BitVector very fast for
1697set operations compared to other containers. Use the BitVector when you expect
1698the number of set bits to be high (IE a dense set).
1699</p>
1700</div>
1701
1702<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1703<h4>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1704 <a name="dss_smallbitvector">SmallBitVector</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1705</h4>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1706
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1707<div>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1708<p> The SmallBitVector container provides the same interface as BitVector, but
1709it is optimized for the case where only a small number of bits, less than
171025 or so, are needed. It also transparently supports larger bit counts, but
1711slightly less efficiently than a plain BitVector, so SmallBitVector should
1712only be used when larger counts are rare.
1713</p>
1714
1715<p>
1716At this time, SmallBitVector does not support set operations (and, or, xor),
1717and its operator[] does not provide an assignable lvalue.
1718</p>
1719</div>
1720
1721<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1722<h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1723 <a name="dss_sparsebitvector">SparseBitVector</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1724</h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1725
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1726<div>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1727<p> The SparseBitVector container is much like BitVector, with one major
1728difference: Only the bits that are set, are stored. This makes the
1729SparseBitVector much more space efficient than BitVector when the set is sparse,
1730as well as making set operations O(number of set bits) instead of O(size of
1731universe). The downside to the SparseBitVector is that setting and testing of random bits is O(N), and on large SparseBitVectors, this can be slower than BitVector. In our implementation, setting or testing bits in sorted order
1732(either forwards or reverse) is O(1) worst case. Testing and setting bits within 128 bits (depends on size) of the current bit is also O(1). As a general statement, testing/setting bits in a SparseBitVector is O(distance away from last set bit).
1733</p>
1734</div>
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]1735
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1736</div>
1737
1738</div>
1739
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1740<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1741<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1742 <a name="common">Helpful Hints for Common Operations</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1743</h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1744<!-- *********************************************************************** -->
1745
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1746<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1747
1748<p>This section describes how to perform some very simple transformations of
1749LLVM code. This is meant to give examples of common idioms used, showing the
1750practical side of LLVM transformations. <p> Because this is a "how-to" section,
1751you should also read about the main classes that you will be working with. The
1752<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
1753and descriptions of the main classes that you should know about.</p>
1754
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1755<!-- NOTE: this section should be heavy on example code -->
1756<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1757<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1758 <a name="inspection">Basic Inspection and Traversal Routines</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1759</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1760
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1761<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1762
1763<p>The LLVM compiler infrastructure have many different data structures that may
1764be traversed. Following the example of the C++ standard template library, the
1765techniques used to traverse these various data structures are all basically the
1766same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
1767method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
1768function returns an iterator pointing to one past the last valid element of the
1769sequence, and there is some <tt>XXXiterator</tt> data type that is common
1770between the two operations.</p>
1771
1772<p>Because the pattern for iteration is common across many different aspects of
1773the program representation, the standard template library algorithms may be used
1774on them, and it is easier to remember how to iterate. First we show a few common
1775examples of the data structures that need to be traversed. Other data
1776structures are traversed in very similar ways.</p>
1777
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1778<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1779<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1780 <a name="iterate_function">Iterating over the </a><a
1781 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
1782 href="#Function"><tt>Function</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1783</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1784
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1785<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1786
1787<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
1788transform in some way; in particular, you'd like to manipulate its
1789<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
1790the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
1791an example that prints the name of a <tt>BasicBlock</tt> and the number of
1792<tt>Instruction</tt>s it contains:</p>
1793
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1794<div class="doc_code">
1795<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1796// <i>func is a pointer to a Function instance</i>
1797for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i)
1798 // <i>Print out the name of the basic block if it has one, and then the</i>
1799 // <i>number of instructions that it contains</i>
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1800 errs() &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has "
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1801 &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1802</pre>
1803</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1804
1805<p>Note that i can be used as if it were a pointer for the purposes of
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]1806invoking member functions of the <tt>Instruction</tt> class. This is
1807because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]1808classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1809exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
1810
1811</div>
1812
1813<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1814<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1815 <a name="iterate_basicblock">Iterating over the </a><a
1816 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1817 href="#BasicBlock"><tt>BasicBlock</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1818</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1819
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1820<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1821
1822<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
1823easy to iterate over the individual instructions that make up
1824<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
1825a <tt>BasicBlock</tt>:</p>
1826
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1827<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1828<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1829// <i>blk is a pointer to a BasicBlock instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1830for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1831 // <i>The next statement works since operator&lt;&lt;(ostream&amp;,...)</i>
1832 // <i>is overloaded for Instruction&amp;</i>
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1833 errs() &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1834</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1835</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1836
1837<p>However, this isn't really the best way to print out the contents of a
1838<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
1839anything you'll care about, you could have just invoked the print routine on the
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1840basic block itself: <tt>errs() &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1841
1842</div>
1843
1844<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1845<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1846 <a name="iterate_institer">Iterating over the </a><a
1847 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1848 href="#Function"><tt>Function</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1849</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1850
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1851<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1852
1853<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
1854<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
1855<tt>InstIterator</tt> should be used instead. You'll need to include <a
1856href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
1857and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1858small example that shows how to dump all instructions in a function to the standard error stream:<p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1859
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1860<div class="doc_code">
1861<pre>
1862#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
1863
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1864// <i>F is a pointer to a Function instance</i>
Chris Lattnerda021aa2008-06-04 18:20:42 +0000[diff] [blame]1865for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1866 errs() &lt;&lt; *I &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1867</pre>
1868</div>
1869
1870<p>Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1871work list with its initial contents. For example, if you wanted to
1872initialize a work list to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1873F, all you would need to do is something like:</p>
1874
1875<div class="doc_code">
1876<pre>
1877std::set&lt;Instruction*&gt; worklist;
Chris Lattnerda021aa2008-06-04 18:20:42 +0000[diff] [blame]1878// or better yet, SmallPtrSet&lt;Instruction*, 64&gt; worklist;
1879
1880for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
1881 worklist.insert(&amp;*I);
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1882</pre>
1883</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1884
1885<p>The STL set <tt>worklist</tt> would now contain all instructions in the
1886<tt>Function</tt> pointed to by F.</p>
1887
1888</div>
1889
1890<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1891<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1892 <a name="iterate_convert">Turning an iterator into a class pointer (and
1893 vice-versa)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1894</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1895
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1896<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1897
1898<p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]1899instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1900a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1901Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1902is a <tt>BasicBlock::const_iterator</tt>:</p>
1903
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1904<div class="doc_code">
1905<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1906Instruction&amp; inst = *i; // <i>Grab reference to instruction reference</i>
1907Instruction* pinst = &amp;*i; // <i>Grab pointer to instruction reference</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1908const Instruction&amp; inst = *j;
1909</pre>
1910</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1911
1912<p>However, the iterators you'll be working with in the LLVM framework are
1913special: they will automatically convert to a ptr-to-instance type whenever they
1914need to. Instead of dereferencing the iterator and then taking the address of
1915the result, you can simply assign the iterator to the proper pointer type and
1916you get the dereference and address-of operation as a result of the assignment
1917(behind the scenes, this is a result of overloading casting mechanisms). Thus
1918the last line of the last example,</p>
1919
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1920<div class="doc_code">
1921<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]1922Instruction *pinst = &amp;*i;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1923</pre>
1924</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1925
1926<p>is semantically equivalent to</p>
1927
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1928<div class="doc_code">
1929<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]1930Instruction *pinst = i;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1931</pre>
1932</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1933
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1934<p>It's also possible to turn a class pointer into the corresponding iterator,
1935and this is a constant time operation (very efficient). The following code
1936snippet illustrates use of the conversion constructors provided by LLVM
1937iterators. By using these, you can explicitly grab the iterator of something
1938without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1939
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1940<div class="doc_code">
1941<pre>
1942void printNextInstruction(Instruction* inst) {
1943 BasicBlock::iterator it(inst);
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1944 ++it; // <i>After this line, it refers to the instruction after *inst</i>
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1945 if (it != inst-&gt;getParent()-&gt;end()) errs() &lt;&lt; *it &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1946}
1947</pre>
1948</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1949
Dan Gohman525bf8e2010-03-26 19:39:05 +0000[diff] [blame]1950<p>Unfortunately, these implicit conversions come at a cost; they prevent
1951these iterators from conforming to standard iterator conventions, and thus
Dan Gohman0d91c112010-03-26 19:51:14 +0000[diff] [blame]1952from being usable with standard algorithms and containers. For example, they
1953prevent the following code, where <tt>B</tt> is a <tt>BasicBlock</tt>,
Dan Gohman525bf8e2010-03-26 19:39:05 +0000[diff] [blame]1954from compiling:</p>
1955
1956<div class="doc_code">
1957<pre>
1958 llvm::SmallVector&lt;llvm::Instruction *, 16&gt;(B-&gt;begin(), B-&gt;end());
1959</pre>
1960</div>
1961
1962<p>Because of this, these implicit conversions may be removed some day,
Dan Gohman0d91c112010-03-26 19:51:14 +0000[diff] [blame]1963and <tt>operator*</tt> changed to return a pointer instead of a reference.</p>
Dan Gohman525bf8e2010-03-26 19:39:05 +0000[diff] [blame]1964
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1965</div>
1966
1967<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1968<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1969 <a name="iterate_complex">Finding call sites: a slightly more complex
1970 example</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1971</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1972
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1973<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1974
1975<p>Say that you're writing a FunctionPass and would like to count all the
1976locations in the entire module (that is, across every <tt>Function</tt>) where a
1977certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
1978learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1979much more straight-forward manner, but this example will allow us to explore how
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1980you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudo-code, this
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1981is what we want to do:</p>
1982
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1983<div class="doc_code">
1984<pre>
1985initialize callCounter to zero
1986for each Function f in the Module
1987 for each BasicBlock b in f
1988 for each Instruction i in b
1989 if (i is a CallInst and calls the given function)
1990 increment callCounter
1991</pre>
1992</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1993
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1994<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1995<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1996override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1997
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1998<div class="doc_code">
1999<pre>
2000Function* targetFunc = ...;
2001
2002class OurFunctionPass : public FunctionPass {
2003 public:
2004 OurFunctionPass(): callCounter(0) { }
2005
2006 virtual runOnFunction(Function&amp; F) {
2007 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
Eric Christopher203e71d2008-11-08 08:20:49 +0000[diff] [blame]2008 for (BasicBlock::iterator i = b-&gt;begin(), ie = b-&gt;end(); i != ie; ++i) {
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2009 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
2010 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2011 // <i>We know we've encountered a call instruction, so we</i>
2012 // <i>need to determine if it's a call to the</i>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2013 // <i>function pointed to by m_func or not.</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2014 if (callInst-&gt;getCalledFunction() == targetFunc)
2015 ++callCounter;
2016 }
2017 }
2018 }
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2019 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2020
2021 private:
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2022 unsigned callCounter;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2023};
2024</pre>
2025</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2026
2027</div>
2028
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]2029<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2030<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2031 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2032</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2033
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2034<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2035
2036<p>You may have noticed that the previous example was a bit oversimplified in
2037that it did not deal with call sites generated by 'invoke' instructions. In
2038this, and in other situations, you may find that you want to treat
2039<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
2040most-specific common base class is <tt>Instruction</tt>, which includes lots of
2041less closely-related things. For these cases, LLVM provides a handy wrapper
2042class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2043href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2044It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
2045methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2046<tt>InvokeInst</tt>s.</p>
2047
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2048<p>This class has "value semantics": it should be passed by value, not by
2049reference and it should not be dynamically allocated or deallocated using
2050<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
2051assignable and constructable, with costs equivalents to that of a bare pointer.
2052If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2053
2054</div>
2055
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]2056<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2057<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2058 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2059</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2060
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2061<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2062
2063<p>Frequently, we might have an instance of the <a
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]2064href="/doxygen/classllvm_1_1Value.html">Value Class</a> and we want to
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2065determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
2066<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
2067For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
2068particular function <tt>foo</tt>. Finding all of the instructions that
2069<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
2070of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2071
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2072<div class="doc_code">
2073<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2074Function *F = ...;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2075
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2076for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i)
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2077 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]2078 errs() &lt;&lt; "F is used in instruction:\n";
2079 errs() &lt;&lt; *Inst &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2080 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2081</pre>
Gabor Greif394fdfb2010-03-26 19:35:48 +0000[diff] [blame]2082</div>
2083
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2084<p>Note that dereferencing a <tt>Value::use_iterator</tt> is not a very cheap
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2085operation. Instead of performing <tt>*i</tt> above several times, consider
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2086doing it only once in the loop body and reusing its result.</p>
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2087
Gabor Greif6091ff32010-03-26 19:04:42 +0000[diff] [blame]2088<p>Alternatively, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2089href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2090<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
2091<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
2092<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
2093all of the values that a particular instruction uses (that is, the operands of
2094the particular <tt>Instruction</tt>):</p>
2095
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2096<div class="doc_code">
2097<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2098Instruction *pi = ...;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2099
2100for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2101 Value *v = *i;
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2102 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2103}
2104</pre>
2105</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2106
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2107<p>Declaring objects as <tt>const</tt> is an important tool of enforcing
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2108mutation free algorithms (such as analyses, etc.). For this purpose above
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2109iterators come in constant flavors as <tt>Value::const_use_iterator</tt>
2110and <tt>Value::const_op_iterator</tt>. They automatically arise when
2111calling <tt>use/op_begin()</tt> on <tt>const Value*</tt>s or
2112<tt>const User*</tt>s respectively. Upon dereferencing, they return
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2113<tt>const Use*</tt>s. Otherwise the above patterns remain unchanged.</p>
2114
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2115</div>
2116
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2117<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2118<h4>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2119 <a name="iterate_preds">Iterating over predecessors &amp;
2120successors of blocks</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2121</h4>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2122
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2123<div>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2124
2125<p>Iterating over the predecessors and successors of a block is quite easy
2126with the routines defined in <tt>"llvm/Support/CFG.h"</tt>. Just use code like
2127this to iterate over all predecessors of BB:</p>
2128
2129<div class="doc_code">
2130<pre>
2131#include "llvm/Support/CFG.h"
2132BasicBlock *BB = ...;
2133
2134for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
2135 BasicBlock *Pred = *PI;
2136 // <i>...</i>
2137}
2138</pre>
2139</div>
2140
2141<p>Similarly, to iterate over successors use
2142succ_iterator/succ_begin/succ_end.</p>
2143
2144</div>
2145
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2146</div>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2147
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2148<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2149<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2150 <a name="simplechanges">Making simple changes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2151</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2152
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2153<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2154
2155<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]2156infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2157transformations, it's fairly common to manipulate the contents of basic
2158blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2159and gives example code.</p>
2160
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2161<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2162<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2163 <a name="schanges_creating">Creating and inserting new
2164 <tt>Instruction</tt>s</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2165</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2166
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2167<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2168
2169<p><i>Instantiating Instructions</i></p>
2170
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2171<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2172constructor for the kind of instruction to instantiate and provide the necessary
2173parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
2174(const-ptr-to) <tt>Type</tt>. Thus:</p>
2175
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2176<div class="doc_code">
2177<pre>
Nick Lewycky10d64b92007-12-03 01:52:52 +0000[diff] [blame]2178AllocaInst* ai = new AllocaInst(Type::Int32Ty);
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2179</pre>
2180</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2181
2182<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]2183one integer in the current stack frame, at run time. Each <tt>Instruction</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2184subclass is likely to have varying default parameters which change the semantics
2185of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2186href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2187Instruction</a> that you're interested in instantiating.</p>
2188
2189<p><i>Naming values</i></p>
2190
2191<p>It is very useful to name the values of instructions when you're able to, as
2192this facilitates the debugging of your transformations. If you end up looking
2193at generated LLVM machine code, you definitely want to have logical names
2194associated with the results of instructions! By supplying a value for the
2195<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
2196associate a logical name with the result of the instruction's execution at
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]2197run time. For example, say that I'm writing a transformation that dynamically
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2198allocates space for an integer on the stack, and that integer is going to be
2199used as some kind of index by some other code. To accomplish this, I place an
2200<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
2201<tt>Function</tt>, and I'm intending to use it within the same
2202<tt>Function</tt>. I might do:</p>
2203
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2204<div class="doc_code">
2205<pre>
Nick Lewycky10d64b92007-12-03 01:52:52 +0000[diff] [blame]2206AllocaInst* pa = new AllocaInst(Type::Int32Ty, 0, "indexLoc");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2207</pre>
2208</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2209
2210<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]2211execution value, which is a pointer to an integer on the run time stack.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2212
2213<p><i>Inserting instructions</i></p>
2214
2215<p>There are essentially two ways to insert an <tt>Instruction</tt>
2216into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
2217
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]2218<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2219 <li>Insertion into an explicit instruction list
2220
2221 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
2222 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
2223 before <tt>*pi</tt>, we do the following: </p>
2224
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2225<div class="doc_code">
2226<pre>
2227BasicBlock *pb = ...;
2228Instruction *pi = ...;
2229Instruction *newInst = new Instruction(...);
2230
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2231pb-&gt;getInstList().insert(pi, newInst); // <i>Inserts newInst before pi in pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2232</pre>
2233</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]2234
2235 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
2236 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
2237 classes provide constructors which take a pointer to a
2238 <tt>BasicBlock</tt> to be appended to. For example code that
2239 looked like: </p>
2240
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2241<div class="doc_code">
2242<pre>
2243BasicBlock *pb = ...;
2244Instruction *newInst = new Instruction(...);
2245
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2246pb-&gt;getInstList().push_back(newInst); // <i>Appends newInst to pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2247</pre>
2248</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]2249
2250 <p>becomes: </p>
2251
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2252<div class="doc_code">
2253<pre>
2254BasicBlock *pb = ...;
2255Instruction *newInst = new Instruction(..., pb);
2256</pre>
2257</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]2258
2259 <p>which is much cleaner, especially if you are creating
2260 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2261
2262 <li>Insertion into an implicit instruction list
2263
2264 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
2265 are implicitly associated with an existing instruction list: the instruction
2266 list of the enclosing basic block. Thus, we could have accomplished the same
2267 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
2268 </p>
2269
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2270<div class="doc_code">
2271<pre>
2272Instruction *pi = ...;
2273Instruction *newInst = new Instruction(...);
2274
2275pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);
2276</pre>
2277</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2278
2279 <p>In fact, this sequence of steps occurs so frequently that the
2280 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
2281 constructors which take (as a default parameter) a pointer to an
2282 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
2283 precede. That is, <tt>Instruction</tt> constructors are capable of
2284 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
2285 provided instruction, immediately before that instruction. Using an
2286 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
2287 parameter, the above code becomes:</p>
2288
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2289<div class="doc_code">
2290<pre>
2291Instruction* pi = ...;
2292Instruction* newInst = new Instruction(..., pi);
2293</pre>
2294</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2295
2296 <p>which is much cleaner, especially if you're creating a lot of
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2297 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2298</ul>
2299
2300</div>
2301
2302<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2303<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2304 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2305</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2306
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2307<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2308
2309<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner49e0ccf2011-03-24 16:13:31 +0000[diff] [blame]2310<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward: just
2311call the instruction's eraseFromParent() method. For example:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2312
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2313<div class="doc_code">
2314<pre>
2315<a href="#Instruction">Instruction</a> *I = .. ;
Chris Lattner9f8ec252008-02-15 22:57:17 +0000[diff] [blame]2316I-&gt;eraseFromParent();
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2317</pre>
2318</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2319
Chris Lattner49e0ccf2011-03-24 16:13:31 +0000[diff] [blame]2320<p>This unlinks the instruction from its containing basic block and deletes
2321it. If you'd just like to unlink the instruction from its containing basic
2322block but not delete it, you can use the <tt>removeFromParent()</tt> method.</p>
2323
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2324</div>
2325
2326<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2327<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2328 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
2329 <tt>Value</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2330</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2331
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2332<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2333
2334<p><i>Replacing individual instructions</i></p>
2335
2336<p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2337permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2338and <tt>ReplaceInstWithInst</tt>.</p>
2339
NAKAMURA Takumi06c6d9a2011-04-18 01:17:51 +0000[diff] [blame]2340<h5><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h5>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2341
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2342<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2343 <li><tt>ReplaceInstWithValue</tt>
2344
Nick Lewyckyb6d1f392008-09-15 06:31:52 +0000[diff] [blame]2345 <p>This function replaces all uses of a given instruction with a value,
2346 and then removes the original instruction. The following example
2347 illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2348 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2349 pointer to an integer.</p>
2350
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2351<div class="doc_code">
2352<pre>
2353AllocaInst* instToReplace = ...;
2354BasicBlock::iterator ii(instToReplace);
2355
2356ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
Daniel Dunbar58c2ac02008-10-03 22:17:25 +0000[diff] [blame]2357 Constant::getNullValue(PointerType::getUnqual(Type::Int32Ty)));
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2358</pre></div></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2359
2360 <li><tt>ReplaceInstWithInst</tt>
2361
2362 <p>This function replaces a particular instruction with another
Nick Lewyckyb6d1f392008-09-15 06:31:52 +0000[diff] [blame]2363 instruction, inserting the new instruction into the basic block at the
2364 location where the old instruction was, and replacing any uses of the old
2365 instruction with the new instruction. The following example illustrates
2366 the replacement of one <tt>AllocaInst</tt> with another.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2367
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2368<div class="doc_code">
2369<pre>
2370AllocaInst* instToReplace = ...;
2371BasicBlock::iterator ii(instToReplace);
2372
2373ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
Nick Lewycky10d64b92007-12-03 01:52:52 +0000[diff] [blame]2374 new AllocaInst(Type::Int32Ty, 0, "ptrToReplacedInt"));
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2375</pre></div></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2376</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2377
2378<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
2379
2380<p>You can use <tt>Value::replaceAllUsesWith</tt> and
2381<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]2382doxygen documentation for the <a href="/doxygen/classllvm_1_1Value.html">Value Class</a>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2383and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2384information.</p>
2385
2386<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
2387include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
2388ReplaceInstWithValue, ReplaceInstWithInst -->
2389
2390</div>
2391
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2392<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2393<h4>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2394 <a name="schanges_deletingGV">Deleting <tt>GlobalVariable</tt>s</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2395</h4>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2396
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2397<div>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2398
Tanya Lattnerc5dfcdb2007-06-20 20:46:37 +0000[diff] [blame]2399<p>Deleting a global variable from a module is just as easy as deleting an
2400Instruction. First, you must have a pointer to the global variable that you wish
2401 to delete. You use this pointer to erase it from its parent, the module.
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2402 For example:</p>
2403
2404<div class="doc_code">
2405<pre>
2406<a href="#GlobalVariable">GlobalVariable</a> *GV = .. ;
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2407
Tanya Lattnerc5dfcdb2007-06-20 20:46:37 +0000[diff] [blame]2408GV-&gt;eraseFromParent();
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2409</pre>
2410</div>
2411
2412</div>
2413
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2414</div>
2415
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2416<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2417<h3>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2418 <a name="create_types">How to Create Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2419</h3>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2420
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2421<div>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2422
2423<p>In generating IR, you may need some complex types. If you know these types
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2424statically, you can use <tt>TypeBuilder&lt;...&gt;::get()</tt>, defined
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2425in <tt>llvm/Support/TypeBuilder.h</tt>, to retrieve them. <tt>TypeBuilder</tt>
2426has two forms depending on whether you're building types for cross-compilation
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2427or native library use. <tt>TypeBuilder&lt;T, true&gt;</tt> requires
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2428that <tt>T</tt> be independent of the host environment, meaning that it's built
2429out of types from
2430the <a href="/doxygen/namespacellvm_1_1types.html"><tt>llvm::types</tt></a>
2431namespace and pointers, functions, arrays, etc. built of
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2432those. <tt>TypeBuilder&lt;T, false&gt;</tt> additionally allows native C types
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2433whose size may depend on the host compiler. For example,</p>
2434
2435<div class="doc_code">
2436<pre>
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2437FunctionType *ft = TypeBuilder&lt;types::i&lt;8&gt;(types::i&lt;32&gt;*), true&gt;::get();
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2438</pre>
2439</div>
2440
2441<p>is easier to read and write than the equivalent</p>
2442
2443<div class="doc_code">
2444<pre>
Owen Anderson5e8c50e2009-06-16 17:40:28 +0000[diff] [blame]2445std::vector&lt;const Type*&gt; params;
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2446params.push_back(PointerType::getUnqual(Type::Int32Ty));
2447FunctionType *ft = FunctionType::get(Type::Int8Ty, params, false);
2448</pre>
2449</div>
2450
2451<p>See the <a href="/doxygen/TypeBuilder_8h-source.html#l00001">class
2452comment</a> for more details.</p>
2453
2454</div>
2455
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2456</div>
2457
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2458<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2459<h2>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2460 <a name="threading">Threads and LLVM</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2461</h2>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2462<!-- *********************************************************************** -->
2463
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2464<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2465<p>
2466This section describes the interaction of the LLVM APIs with multithreading,
2467both on the part of client applications, and in the JIT, in the hosted
2468application.
2469</p>
2470
2471<p>
2472Note that LLVM's support for multithreading is still relatively young. Up
2473through version 2.5, the execution of threaded hosted applications was
2474supported, but not threaded client access to the APIs. While this use case is
2475now supported, clients <em>must</em> adhere to the guidelines specified below to
2476ensure proper operation in multithreaded mode.
2477</p>
2478
2479<p>
2480Note that, on Unix-like platforms, LLVM requires the presence of GCC's atomic
2481intrinsics in order to support threaded operation. If you need a
2482multhreading-capable LLVM on a platform without a suitably modern system
2483compiler, consider compiling LLVM and LLVM-GCC in single-threaded mode, and
2484using the resultant compiler to build a copy of LLVM with multithreading
2485support.
2486</p>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2487
2488<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2489<h3>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2490 <a name="startmultithreaded">Entering and Exiting Multithreaded Mode</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2491</h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2492
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2493<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2494
2495<p>
2496In order to properly protect its internal data structures while avoiding
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2497excessive locking overhead in the single-threaded case, the LLVM must intialize
2498certain data structures necessary to provide guards around its internals. To do
2499so, the client program must invoke <tt>llvm_start_multithreaded()</tt> before
2500making any concurrent LLVM API calls. To subsequently tear down these
2501structures, use the <tt>llvm_stop_multithreaded()</tt> call. You can also use
2502the <tt>llvm_is_multithreaded()</tt> call to check the status of multithreaded
2503mode.
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2504</p>
2505
2506<p>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2507Note that both of these calls must be made <em>in isolation</em>. That is to
2508say that no other LLVM API calls may be executing at any time during the
2509execution of <tt>llvm_start_multithreaded()</tt> or <tt>llvm_stop_multithreaded
2510</tt>. It's is the client's responsibility to enforce this isolation.
2511</p>
2512
2513<p>
2514The return value of <tt>llvm_start_multithreaded()</tt> indicates the success or
2515failure of the initialization. Failure typically indicates that your copy of
2516LLVM was built without multithreading support, typically because GCC atomic
2517intrinsics were not found in your system compiler. In this case, the LLVM API
2518will not be safe for concurrent calls. However, it <em>will</em> be safe for
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2519hosting threaded applications in the JIT, though <a href="#jitthreading">care
2520must be taken</a> to ensure that side exits and the like do not accidentally
2521result in concurrent LLVM API calls.
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2522</p>
2523</div>
2524
2525<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2526<h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2527 <a name="shutdown">Ending Execution with <tt>llvm_shutdown()</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2528</h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2529
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2530<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2531<p>
2532When you are done using the LLVM APIs, you should call <tt>llvm_shutdown()</tt>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2533to deallocate memory used for internal structures. This will also invoke
2534<tt>llvm_stop_multithreaded()</tt> if LLVM is operating in multithreaded mode.
2535As such, <tt>llvm_shutdown()</tt> requires the same isolation guarantees as
2536<tt>llvm_stop_multithreaded()</tt>.
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2537</p>
2538
2539<p>
2540Note that, if you use scope-based shutdown, you can use the
2541<tt>llvm_shutdown_obj</tt> class, which calls <tt>llvm_shutdown()</tt> in its
2542destructor.
2543</div>
2544
2545<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2546<h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2547 <a name="managedstatic">Lazy Initialization with <tt>ManagedStatic</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2548</h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2549
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2550<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2551<p>
2552<tt>ManagedStatic</tt> is a utility class in LLVM used to implement static
2553initialization of static resources, such as the global type tables. Before the
2554invocation of <tt>llvm_shutdown()</tt>, it implements a simple lazy
2555initialization scheme. Once <tt>llvm_start_multithreaded()</tt> returns,
2556however, it uses double-checked locking to implement thread-safe lazy
2557initialization.
2558</p>
2559
2560<p>
2561Note that, because no other threads are allowed to issue LLVM API calls before
2562<tt>llvm_start_multithreaded()</tt> returns, it is possible to have
2563<tt>ManagedStatic</tt>s of <tt>llvm::sys::Mutex</tt>s.
2564</p>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2565
2566<p>
2567The <tt>llvm_acquire_global_lock()</tt> and <tt>llvm_release_global_lock</tt>
2568APIs provide access to the global lock used to implement the double-checked
2569locking for lazy initialization. These should only be used internally to LLVM,
2570and only if you know what you're doing!
2571</p>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2572</div>
2573
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2574<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2575<h3>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2576 <a name="llvmcontext">Achieving Isolation with <tt>LLVMContext</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2577</h3>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2578
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2579<div>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2580<p>
2581<tt>LLVMContext</tt> is an opaque class in the LLVM API which clients can use
2582to operate multiple, isolated instances of LLVM concurrently within the same
2583address space. For instance, in a hypothetical compile-server, the compilation
2584of an individual translation unit is conceptually independent from all the
2585others, and it would be desirable to be able to compile incoming translation
2586units concurrently on independent server threads. Fortunately,
2587<tt>LLVMContext</tt> exists to enable just this kind of scenario!
2588</p>
2589
2590<p>
2591Conceptually, <tt>LLVMContext</tt> provides isolation. Every LLVM entity
2592(<tt>Module</tt>s, <tt>Value</tt>s, <tt>Type</tt>s, <tt>Constant</tt>s, etc.)
Chris Lattner38eee3c2009-08-20 03:10:14 +0000[diff] [blame]2593in LLVM's in-memory IR belongs to an <tt>LLVMContext</tt>. Entities in
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2594different contexts <em>cannot</em> interact with each other: <tt>Module</tt>s in
2595different contexts cannot be linked together, <tt>Function</tt>s cannot be added
2596to <tt>Module</tt>s in different contexts, etc. What this means is that is is
2597safe to compile on multiple threads simultaneously, as long as no two threads
2598operate on entities within the same context.
2599</p>
2600
2601<p>
2602In practice, very few places in the API require the explicit specification of a
2603<tt>LLVMContext</tt>, other than the <tt>Type</tt> creation/lookup APIs.
2604Because every <tt>Type</tt> carries a reference to its owning context, most
2605other entities can determine what context they belong to by looking at their
2606own <tt>Type</tt>. If you are adding new entities to LLVM IR, please try to
2607maintain this interface design.
2608</p>
2609
2610<p>
2611For clients that do <em>not</em> require the benefits of isolation, LLVM
2612provides a convenience API <tt>getGlobalContext()</tt>. This returns a global,
2613lazily initialized <tt>LLVMContext</tt> that may be used in situations where
2614isolation is not a concern.
2615</p>
2616</div>
2617
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2618<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2619<h3>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2620 <a name="jitthreading">Threads and the JIT</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2621</h3>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2622
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2623<div>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2624<p>
2625LLVM's "eager" JIT compiler is safe to use in threaded programs. Multiple
2626threads can call <tt>ExecutionEngine::getPointerToFunction()</tt> or
2627<tt>ExecutionEngine::runFunction()</tt> concurrently, and multiple threads can
2628run code output by the JIT concurrently. The user must still ensure that only
2629one thread accesses IR in a given <tt>LLVMContext</tt> while another thread
2630might be modifying it. One way to do that is to always hold the JIT lock while
2631accessing IR outside the JIT (the JIT <em>modifies</em> the IR by adding
2632<tt>CallbackVH</tt>s). Another way is to only
2633call <tt>getPointerToFunction()</tt> from the <tt>LLVMContext</tt>'s thread.
2634</p>
2635
2636<p>When the JIT is configured to compile lazily (using
2637<tt>ExecutionEngine::DisableLazyCompilation(false)</tt>), there is currently a
2638<a href="http://llvm.org/bugs/show_bug.cgi?id=5184">race condition</a> in
2639updating call sites after a function is lazily-jitted. It's still possible to
2640use the lazy JIT in a threaded program if you ensure that only one thread at a
2641time can call any particular lazy stub and that the JIT lock guards any IR
2642access, but we suggest using only the eager JIT in threaded programs.
2643</p>
2644</div>
2645
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2646</div>
2647
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2648<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2649<h2>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2650 <a name="advanced">Advanced Topics</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2651</h2>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2652<!-- *********************************************************************** -->
2653
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2654<div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]2655<p>
2656This section describes some of the advanced or obscure API's that most clients
2657do not need to be aware of. These API's tend manage the inner workings of the
2658LLVM system, and only need to be accessed in unusual circumstances.
2659</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2660
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2661
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]2662<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2663<h3>
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2664 <a name="SymbolTable">The <tt>ValueSymbolTable</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2665</h3>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]2666
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2667<div>
Chris Lattner263a98e2007-02-16 04:37:31 +0000[diff] [blame]2668<p>The <tt><a href="http://llvm.org/doxygen/classllvm_1_1ValueSymbolTable.html">
2669ValueSymbolTable</a></tt> class provides a symbol table that the <a
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2670href="#Function"><tt>Function</tt></a> and <a href="#Module">
Chris Lattner263a98e2007-02-16 04:37:31 +0000[diff] [blame]2671<tt>Module</tt></a> classes use for naming value definitions. The symbol table
2672can provide a name for any <a href="#Value"><tt>Value</tt></a>.
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2673</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2674
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]2675<p>Note that the <tt>SymbolTable</tt> class should not be directly accessed
2676by most clients. It should only be used when iteration over the symbol table
2677names themselves are required, which is very special purpose. Note that not
2678all LLVM
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2679<tt><a href="#Value">Value</a></tt>s have names, and those without names (i.e. they have
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2680an empty name) do not exist in the symbol table.
2681</p>
2682
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2683<p>Symbol tables support iteration over the values in the symbol
Chris Lattner263a98e2007-02-16 04:37:31 +0000[diff] [blame]2684table with <tt>begin/end/iterator</tt> and supports querying to see if a
2685specific name is in the symbol table (with <tt>lookup</tt>). The
2686<tt>ValueSymbolTable</tt> class exposes no public mutator methods, instead,
2687simply call <tt>setName</tt> on a value, which will autoinsert it into the
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2688appropriate symbol table.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2689
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2690</div>
2691
2692
2693
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2694<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2695<h3>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2696 <a name="UserLayout">The <tt>User</tt> and owned <tt>Use</tt> classes' memory layout</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2697</h3>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2698
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2699<div>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2700<p>The <tt><a href="http://llvm.org/doxygen/classllvm_1_1User.html">
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2701User</a></tt> class provides a basis for expressing the ownership of <tt>User</tt>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2702towards other <tt><a href="http://llvm.org/doxygen/classllvm_1_1Value.html">
2703Value</a></tt>s. The <tt><a href="http://llvm.org/doxygen/classllvm_1_1Use.html">
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2704Use</a></tt> helper class is employed to do the bookkeeping and to facilitate <i>O(1)</i>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2705addition and removal.</p>
2706
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2707<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2708<h4>
2709 <a name="Use2User">
2710 Interaction and relationship between <tt>User</tt> and <tt>Use</tt> objects
2711 </a>
2712</h4>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2713
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2714<div>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2715<p>
2716A subclass of <tt>User</tt> can choose between incorporating its <tt>Use</tt> objects
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2717or refer to them out-of-line by means of a pointer. A mixed variant
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2718(some <tt>Use</tt>s inline others hung off) is impractical and breaks the invariant
2719that the <tt>Use</tt> objects belonging to the same <tt>User</tt> form a contiguous array.
2720</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2721
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2722<p>
2723We have 2 different layouts in the <tt>User</tt> (sub)classes:
2724<ul>
2725<li><p>Layout a)
2726The <tt>Use</tt> object(s) are inside (resp. at fixed offset) of the <tt>User</tt>
2727object and there are a fixed number of them.</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2728
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2729<li><p>Layout b)
2730The <tt>Use</tt> object(s) are referenced by a pointer to an
2731array from the <tt>User</tt> object and there may be a variable
2732number of them.</p>
2733</ul>
2734<p>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2735As of v2.4 each layout still possesses a direct pointer to the
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2736start of the array of <tt>Use</tt>s. Though not mandatory for layout a),
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2737we stick to this redundancy for the sake of simplicity.
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2738The <tt>User</tt> object also stores the number of <tt>Use</tt> objects it
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2739has. (Theoretically this information can also be calculated
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2740given the scheme presented below.)</p>
2741<p>
2742Special forms of allocation operators (<tt>operator new</tt>)
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2743enforce the following memory layouts:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2744
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2745<ul>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2746<li><p>Layout a) is modelled by prepending the <tt>User</tt> object by the <tt>Use[]</tt> array.</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2747
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2748<pre>
2749...---.---.---.---.-------...
2750 | P | P | P | P | User
2751'''---'---'---'---'-------'''
2752</pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2753
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2754<li><p>Layout b) is modelled by pointing at the <tt>Use[]</tt> array.</p>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2755<pre>
2756.-------...
2757| User
2758'-------'''
2759 |
2760 v
2761 .---.---.---.---...
2762 | P | P | P | P |
2763 '---'---'---'---'''
2764</pre>
2765</ul>
2766<i>(In the above figures '<tt>P</tt>' stands for the <tt>Use**</tt> that
2767 is stored in each <tt>Use</tt> object in the member <tt>Use::Prev</tt>)</i>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2768
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2769</div>
2770
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2771<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2772<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2773 <a name="Waymarking">The waymarking algorithm</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2774</h4>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2775
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2776<div>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2777<p>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2778Since the <tt>Use</tt> objects are deprived of the direct (back)pointer to
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2779their <tt>User</tt> objects, there must be a fast and exact method to
2780recover it. This is accomplished by the following scheme:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2781
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2782A bit-encoding in the 2 LSBits (least significant bits) of the <tt>Use::Prev</tt> allows to find the
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2783start of the <tt>User</tt> object:
2784<ul>
2785<li><tt>00</tt> &mdash;&gt; binary digit 0</li>
2786<li><tt>01</tt> &mdash;&gt; binary digit 1</li>
2787<li><tt>10</tt> &mdash;&gt; stop and calculate (<tt>s</tt>)</li>
2788<li><tt>11</tt> &mdash;&gt; full stop (<tt>S</tt>)</li>
2789</ul>
2790<p>
2791Given a <tt>Use*</tt>, all we have to do is to walk till we get
2792a stop and we either have a <tt>User</tt> immediately behind or
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2793we have to walk to the next stop picking up digits
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2794and calculating the offset:</p>
2795<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2796.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.----------------
2797| 1 | s | 1 | 0 | 1 | 0 | s | 1 | 1 | 0 | s | 1 | 1 | s | 1 | S | User (or User*)
2798'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'----------------
2799 |+15 |+10 |+6 |+3 |+1
2800 | | | | |__>
2801 | | | |__________>
2802 | | |______________________>
2803 | |______________________________________>
2804 |__________________________________________________________>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2805</pre>
2806<p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2807Only the significant number of bits need to be stored between the
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2808stops, so that the <i>worst case is 20 memory accesses</i> when there are
28091000 <tt>Use</tt> objects associated with a <tt>User</tt>.</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2810
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2811</div>
2812
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2813<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2814<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2815 <a name="ReferenceImpl">Reference implementation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2816</h4>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2817
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2818<div>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2819<p>
2820The following literate Haskell fragment demonstrates the concept:</p>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2821
2822<div class="doc_code">
2823<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2824> import Test.QuickCheck
2825>
2826> digits :: Int -> [Char] -> [Char]
2827> digits 0 acc = '0' : acc
2828> digits 1 acc = '1' : acc
2829> digits n acc = digits (n `div` 2) $ digits (n `mod` 2) acc
2830>
2831> dist :: Int -> [Char] -> [Char]
2832> dist 0 [] = ['S']
2833> dist 0 acc = acc
2834> dist 1 acc = let r = dist 0 acc in 's' : digits (length r) r
2835> dist n acc = dist (n - 1) $ dist 1 acc
2836>
2837> takeLast n ss = reverse $ take n $ reverse ss
2838>
2839> test = takeLast 40 $ dist 20 []
2840>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2841</pre>
2842</div>
2843<p>
2844Printing &lt;test&gt; gives: <tt>"1s100000s11010s10100s1111s1010s110s11s1S"</tt></p>
2845<p>
2846The reverse algorithm computes the length of the string just by examining
2847a certain prefix:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2848
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2849<div class="doc_code">
2850<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2851> pref :: [Char] -> Int
2852> pref "S" = 1
2853> pref ('s':'1':rest) = decode 2 1 rest
2854> pref (_:rest) = 1 + pref rest
2855>
2856> decode walk acc ('0':rest) = decode (walk + 1) (acc * 2) rest
2857> decode walk acc ('1':rest) = decode (walk + 1) (acc * 2 + 1) rest
2858> decode walk acc _ = walk + acc
2859>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2860</pre>
2861</div>
2862<p>
2863Now, as expected, printing &lt;pref test&gt; gives <tt>40</tt>.</p>
2864<p>
2865We can <i>quickCheck</i> this with following property:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2866
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2867<div class="doc_code">
2868<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2869> testcase = dist 2000 []
2870> testcaseLength = length testcase
2871>
2872> identityProp n = n > 0 && n <= testcaseLength ==> length arr == pref arr
2873> where arr = takeLast n testcase
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2874>
2875</pre>
2876</div>
2877<p>
2878As expected &lt;quickCheck identityProp&gt; gives:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2879
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2880<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2881*Main> quickCheck identityProp
2882OK, passed 100 tests.
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2883</pre>
2884<p>
2885Let's be a bit more exhaustive:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2886
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2887<div class="doc_code">
2888<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2889>
2890> deepCheck p = check (defaultConfig { configMaxTest = 500 }) p
2891>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2892</pre>
2893</div>
2894<p>
2895And here is the result of &lt;deepCheck identityProp&gt;:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2896
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2897<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2898*Main> deepCheck identityProp
2899OK, passed 500 tests.
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2900</pre>
2901
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2902</div>
2903
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2904<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2905<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2906 <a name="Tagging">Tagging considerations</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2907</h4>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2908
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2909<div>
2910
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2911<p>
2912To maintain the invariant that the 2 LSBits of each <tt>Use**</tt> in <tt>Use</tt>
2913never change after being set up, setters of <tt>Use::Prev</tt> must re-tag the
2914new <tt>Use**</tt> on every modification. Accordingly getters must strip the
2915tag bits.</p>
2916<p>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2917For layout b) instead of the <tt>User</tt> we find a pointer (<tt>User*</tt> with LSBit set).
2918Following this pointer brings us to the <tt>User</tt>. A portable trick ensures
2919that the first bytes of <tt>User</tt> (if interpreted as a pointer) never has
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2920the LSBit set. (Portability is relying on the fact that all known compilers place the
2921<tt>vptr</tt> in the first word of the instances.)</p>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2922
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2923</div>
2924
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2925</div>
2926
2927</div>
2928
2929<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2930<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2931 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2932</h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2933<!-- *********************************************************************** -->
2934
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2935<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2936<p><tt>#include "<a href="/doxygen/Type_8h-source.html">llvm/Type.h</a>"</tt>
2937<br>doxygen info: <a href="/doxygen/classllvm_1_1Type.html">Type Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2938
2939<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2940being inspected or transformed. The core LLVM classes are defined in
2941header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2942the <tt>lib/VMCore</tt> directory.</p>
2943
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2944<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2945<h3>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2946 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2947</h3>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2948
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2949<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2950
2951 <p><tt>Type</tt> is a superclass of all type classes. Every <tt>Value</tt> has
2952 a <tt>Type</tt>. <tt>Type</tt> cannot be instantiated directly but only
2953 through its subclasses. Certain primitive types (<tt>VoidType</tt>,
2954 <tt>LabelType</tt>, <tt>FloatType</tt> and <tt>DoubleType</tt>) have hidden
2955 subclasses. They are hidden because they offer no useful functionality beyond
2956 what the <tt>Type</tt> class offers except to distinguish themselves from
2957 other subclasses of <tt>Type</tt>.</p>
2958 <p>All other types are subclasses of <tt>DerivedType</tt>. Types can be
2959 named, but this is not a requirement. There exists exactly
2960 one instance of a given shape at any one time. This allows type equality to
2961 be performed with address equality of the Type Instance. That is, given two
2962 <tt>Type*</tt> values, the types are identical if the pointers are identical.
2963 </p>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2964
2965<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2966<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2967 <a name="m_Type">Important Public Methods</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2968</h4>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2969
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2970<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2971
2972<ul>
Duncan Sandsb0bc6c32010-02-15 16:12:20 +0000[diff] [blame]2973 <li><tt>bool isIntegerTy() const</tt>: Returns true for any integer type.</li>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2974
Duncan Sandsb0bc6c32010-02-15 16:12:20 +0000[diff] [blame]2975 <li><tt>bool isFloatingPointTy()</tt>: Return true if this is one of the five
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2976 floating point types.</li>
2977
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2978 <li><tt>bool isSized()</tt>: Return true if the type has known size. Things
2979 that don't have a size are abstract types, labels and void.</li>
2980
2981</ul>
2982</div>
2983
2984<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2985<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2986 <a name="derivedtypes">Important Derived Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2987</h4>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2988<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2989<dl>
2990 <dt><tt>IntegerType</tt></dt>
2991 <dd>Subclass of DerivedType that represents integer types of any bit width.
2992 Any bit width between <tt>IntegerType::MIN_INT_BITS</tt> (1) and
2993 <tt>IntegerType::MAX_INT_BITS</tt> (~8 million) can be represented.
2994 <ul>
2995 <li><tt>static const IntegerType* get(unsigned NumBits)</tt>: get an integer
2996 type of a specific bit width.</li>
2997 <li><tt>unsigned getBitWidth() const</tt>: Get the bit width of an integer
2998 type.</li>
2999 </ul>
3000 </dd>
3001 <dt><tt>SequentialType</tt></dt>
Tobias Grosserd475c102011-07-12 11:37:02 +0000[diff] [blame]3002 <dd>This is subclassed by ArrayType, PointerType and VectorType.
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3003 <ul>
3004 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
3005 of the elements in the sequential type. </li>
3006 </ul>
3007 </dd>
3008 <dt><tt>ArrayType</tt></dt>
3009 <dd>This is a subclass of SequentialType and defines the interface for array
3010 types.
3011 <ul>
3012 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
3013 elements in the array. </li>
3014 </ul>
3015 </dd>
3016 <dt><tt>PointerType</tt></dt>
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]3017 <dd>Subclass of SequentialType for pointer types.</dd>
Reid Spencer9d6565a2007-02-15 02:26:10 +0000[diff] [blame]3018 <dt><tt>VectorType</tt></dt>
Reid Spencer485bad12007-02-15 03:07:05 +0000[diff] [blame]3019 <dd>Subclass of SequentialType for vector types. A
3020 vector type is similar to an ArrayType but is distinguished because it is
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3021 a first class type whereas ArrayType is not. Vector types are used for
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3022 vector operations and are usually small vectors of of an integer or floating
3023 point type.</dd>
3024 <dt><tt>StructType</tt></dt>
3025 <dd>Subclass of DerivedTypes for struct types.</dd>
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]3026 <dt><tt><a name="FunctionType">FunctionType</a></tt></dt>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3027 <dd>Subclass of DerivedTypes for function types.
3028 <ul>
Dan Gohman4bb31bf2010-03-30 20:04:57 +0000[diff] [blame]3029 <li><tt>bool isVarArg() const</tt>: Returns true if it's a vararg
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3030 function</li>
3031 <li><tt> const Type * getReturnType() const</tt>: Returns the
3032 return type of the function.</li>
3033 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
3034 the type of the ith parameter.</li>
3035 <li><tt> const unsigned getNumParams() const</tt>: Returns the
3036 number of formal parameters.</li>
3037 </ul>
3038 </dd>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3039</dl>
3040</div>
3041
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3042</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3043
3044<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3045<h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3046 <a name="Module">The <tt>Module</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3047</h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3048
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3049<div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3050
3051<p><tt>#include "<a
3052href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
3053<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
3054
3055<p>The <tt>Module</tt> class represents the top level structure present in LLVM
3056programs. An LLVM module is effectively either a translation unit of the
3057original program or a combination of several translation units merged by the
3058linker. The <tt>Module</tt> class keeps track of a list of <a
3059href="#Function"><tt>Function</tt></a>s, a list of <a
3060href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
3061href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
3062helpful member functions that try to make common operations easy.</p>
3063
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3064<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3065<h4>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3066 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3067</h4>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3068
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3069<div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3070
3071<ul>
3072 <li><tt>Module::Module(std::string name = "")</tt></li>
3073</ul>
3074
3075<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
3076provide a name for it (probably based on the name of the translation unit).</p>
3077
3078<ul>
3079 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
3080 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
3081
3082 <tt>begin()</tt>, <tt>end()</tt>
3083 <tt>size()</tt>, <tt>empty()</tt>
3084
3085 <p>These are forwarding methods that make it easy to access the contents of
3086 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
3087 list.</p></li>
3088
3089 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
3090
3091 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
3092 necessary to use when you need to update the list or perform a complex
3093 action that doesn't have a forwarding method.</p>
3094
3095 <p><!-- Global Variable --></p></li>
3096</ul>
3097
3098<hr>
3099
3100<ul>
3101 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
3102
3103 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
3104
3105 <tt>global_begin()</tt>, <tt>global_end()</tt>
3106 <tt>global_size()</tt>, <tt>global_empty()</tt>
3107
3108 <p> These are forwarding methods that make it easy to access the contents of
3109 a <tt>Module</tt> object's <a
3110 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
3111
3112 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
3113
3114 <p>Returns the list of <a
3115 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
3116 use when you need to update the list or perform a complex action that
3117 doesn't have a forwarding method.</p>
3118
3119 <p><!-- Symbol table stuff --> </p></li>
3120</ul>
3121
3122<hr>
3123
3124<ul>
3125 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
3126
3127 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
3128 for this <tt>Module</tt>.</p>
3129
3130 <p><!-- Convenience methods --></p></li>
3131</ul>
3132
3133<hr>
3134
3135<ul>
3136 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
3137 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
3138
3139 <p>Look up the specified function in the <tt>Module</tt> <a
3140 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
3141 <tt>null</tt>.</p></li>
3142
3143 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
3144 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
3145
3146 <p>Look up the specified function in the <tt>Module</tt> <a
3147 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
3148 external declaration for the function and return it.</p></li>
3149
3150 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
3151
3152 <p>If there is at least one entry in the <a
3153 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
3154 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
3155 string.</p></li>
3156
3157 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
3158 href="#Type">Type</a> *Ty)</tt>
3159
3160 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
3161 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
3162 name, true is returned and the <a
3163 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
3164</ul>
3165
3166</div>
3167
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3168</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3169
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3170<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3171<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3172 <a name="Value">The <tt>Value</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3173</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3174
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3175<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3176
3177<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
3178<br>
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]3179doxygen info: <a href="/doxygen/classllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3180
3181<p>The <tt>Value</tt> class is the most important class in the LLVM Source
3182base. It represents a typed value that may be used (among other things) as an
3183operand to an instruction. There are many different types of <tt>Value</tt>s,
3184such as <a href="#Constant"><tt>Constant</tt></a>s,<a
3185href="#Argument"><tt>Argument</tt></a>s. Even <a
3186href="#Instruction"><tt>Instruction</tt></a>s and <a
3187href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
3188
3189<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
3190for a program. For example, an incoming argument to a function (represented
3191with an instance of the <a href="#Argument">Argument</a> class) is "used" by
3192every instruction in the function that references the argument. To keep track
3193of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
3194href="#User"><tt>User</tt></a>s that is using it (the <a
3195href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
3196graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
3197def-use information in the program, and is accessible through the <tt>use_</tt>*
3198methods, shown below.</p>
3199
3200<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
3201and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
3202method. In addition, all LLVM values can be named. The "name" of the
3203<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
3204
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]3205<div class="doc_code">
3206<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]3207%<b>foo</b> = add i32 1, 2
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]3208</pre>
3209</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3210
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]3211<p><a name="nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3212that the name of any value may be missing (an empty string), so names should
3213<b>ONLY</b> be used for debugging (making the source code easier to read,
3214debugging printouts), they should not be used to keep track of values or map
3215between them. For this purpose, use a <tt>std::map</tt> of pointers to the
3216<tt>Value</tt> itself instead.</p>
3217
3218<p>One important aspect of LLVM is that there is no distinction between an SSA
3219variable and the operation that produces it. Because of this, any reference to
3220the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]3221argument, for example) is represented as a direct pointer to the instance of
3222the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3223represents this value. Although this may take some getting used to, it
3224simplifies the representation and makes it easier to manipulate.</p>
3225
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3226<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3227<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3228 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3229</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3230
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3231<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3232
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3233<ul>
3234 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
3235use-list<br>
Gabor Greifbbbf9a22010-03-26 19:59:25 +0000[diff] [blame]3236 <tt>Value::const_use_iterator</tt> - Typedef for const_iterator over
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3237the use-list<br>
3238 <tt>unsigned use_size()</tt> - Returns the number of users of the
3239value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3240 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3241 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
3242the use-list.<br>
3243 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
3244use-list.<br>
3245 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
3246element in the list.
3247 <p> These methods are the interface to access the def-use
3248information in LLVM. As with all other iterators in LLVM, the naming
3249conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3250 </li>
3251 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3252 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3253 </li>
3254 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3255 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3256 <tt>void setName(const std::string &amp;Name)</tt>
3257 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
3258be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3259 </li>
3260 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3261
3262 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
3263 href="#User"><tt>User</tt>s</a> of the current value to refer to
3264 "<tt>V</tt>" instead. For example, if you detect that an instruction always
3265 produces a constant value (for example through constant folding), you can
3266 replace all uses of the instruction with the constant like this:</p>
3267
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]3268<div class="doc_code">
3269<pre>
3270Inst-&gt;replaceAllUsesWith(ConstVal);
3271</pre>
3272</div>
3273
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3274</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3275
3276</div>
3277
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3278</div>
3279
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3280<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3281<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3282 <a name="User">The <tt>User</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3283</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3284
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3285<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3286
3287<p>
3288<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]3289doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3290Superclass: <a href="#Value"><tt>Value</tt></a></p>
3291
3292<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
3293refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
3294that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
3295referring to. The <tt>User</tt> class itself is a subclass of
3296<tt>Value</tt>.</p>
3297
3298<p>The operands of a <tt>User</tt> point directly to the LLVM <a
3299href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
3300Single Assignment (SSA) form, there can only be one definition referred to,
3301allowing this direct connection. This connection provides the use-def
3302information in LLVM.</p>
3303
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3304<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3305<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3306 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3307</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3308
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3309<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3310
3311<p>The <tt>User</tt> class exposes the operand list in two ways: through
3312an index access interface and through an iterator based interface.</p>
3313
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3314<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3315 <li><tt>Value *getOperand(unsigned i)</tt><br>
3316 <tt>unsigned getNumOperands()</tt>
3317 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3318convenient form for direct access.</p></li>
3319
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3320 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
3321list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]3322 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
3323the operand list.<br>
3324 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3325operand list.
3326 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3327the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3328</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3329
3330</div>
3331
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3332</div>
3333
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3334<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3335<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3336 <a name="Instruction">The <tt>Instruction</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3337</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3338
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3339<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3340
3341<p><tt>#include "</tt><tt><a
3342href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]3343doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3344Superclasses: <a href="#User"><tt>User</tt></a>, <a
3345href="#Value"><tt>Value</tt></a></p>
3346
3347<p>The <tt>Instruction</tt> class is the common base class for all LLVM
3348instructions. It provides only a few methods, but is a very commonly used
3349class. The primary data tracked by the <tt>Instruction</tt> class itself is the
3350opcode (instruction type) and the parent <a
3351href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
3352into. To represent a specific type of instruction, one of many subclasses of
3353<tt>Instruction</tt> are used.</p>
3354
3355<p> Because the <tt>Instruction</tt> class subclasses the <a
3356href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
3357way as for other <a href="#User"><tt>User</tt></a>s (with the
3358<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
3359<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
3360the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
3361file contains some meta-data about the various different types of instructions
3362in LLVM. It describes the enum values that are used as opcodes (for example
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]3363<tt>Instruction::Add</tt> and <tt>Instruction::ICmp</tt>), as well as the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3364concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
3365example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]3366href="#CmpInst">CmpInst</a></tt>). Unfortunately, the use of macros in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3367this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]3368<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3369
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3370<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3371<h4>
3372 <a name="s_Instruction">
3373 Important Subclasses of the <tt>Instruction</tt> class
3374 </a>
3375</h4>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3376<div>
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]3377 <ul>
3378 <li><tt><a name="BinaryOperator">BinaryOperator</a></tt>
3379 <p>This subclasses represents all two operand instructions whose operands
3380 must be the same type, except for the comparison instructions.</p></li>
3381 <li><tt><a name="CastInst">CastInst</a></tt>
3382 <p>This subclass is the parent of the 12 casting instructions. It provides
3383 common operations on cast instructions.</p>
3384 <li><tt><a name="CmpInst">CmpInst</a></tt>
3385 <p>This subclass respresents the two comparison instructions,
3386 <a href="LangRef.html#i_icmp">ICmpInst</a> (integer opreands), and
3387 <a href="LangRef.html#i_fcmp">FCmpInst</a> (floating point operands).</p>
3388 <li><tt><a name="TerminatorInst">TerminatorInst</a></tt>
3389 <p>This subclass is the parent of all terminator instructions (those which
3390 can terminate a block).</p>
3391 </ul>
3392 </div>
3393
3394<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3395<h4>
3396 <a name="m_Instruction">
3397 Important Public Members of the <tt>Instruction</tt> class
3398 </a>
3399</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3400
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3401<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3402
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3403<ul>
3404 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3405 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
3406this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3407 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3408 <p>Returns true if the instruction writes to memory, i.e. it is a
3409 <tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3410 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3411 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3412 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3413 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3414in all ways to the original except that the instruction has no parent
3415(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3416and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3417</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3418
3419</div>
3420
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3421</div>
3422
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3423<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3424<h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3425 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3426</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3427
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3428<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3429
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3430<p>Constant represents a base class for different types of constants. It
3431is subclassed by ConstantInt, ConstantArray, etc. for representing
3432the various types of Constants. <a href="#GlobalValue">GlobalValue</a> is also
3433a subclass, which represents the address of a global variable or function.
3434</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3435
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3436<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3437<h4>Important Subclasses of Constant</h4>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3438<div>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3439<ul>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3440 <li>ConstantInt : This subclass of Constant represents an integer constant of
3441 any width.
3442 <ul>
Reid Spencer97b4ee32007-03-01 21:05:33 +0000[diff] [blame]3443 <li><tt>const APInt&amp; getValue() const</tt>: Returns the underlying
3444 value of this constant, an APInt value.</li>
3445 <li><tt>int64_t getSExtValue() const</tt>: Converts the underlying APInt
3446 value to an int64_t via sign extension. If the value (not the bit width)
3447 of the APInt is too large to fit in an int64_t, an assertion will result.
3448 For this reason, use of this method is discouraged.</li>
3449 <li><tt>uint64_t getZExtValue() const</tt>: Converts the underlying APInt
3450 value to a uint64_t via zero extension. IF the value (not the bit width)
3451 of the APInt is too large to fit in a uint64_t, an assertion will result.
Reid Spencer4474d872007-03-02 01:31:31 +0000[diff] [blame]3452 For this reason, use of this method is discouraged.</li>
Reid Spencer97b4ee32007-03-01 21:05:33 +0000[diff] [blame]3453 <li><tt>static ConstantInt* get(const APInt&amp; Val)</tt>: Returns the
3454 ConstantInt object that represents the value provided by <tt>Val</tt>.
3455 The type is implied as the IntegerType that corresponds to the bit width
3456 of <tt>Val</tt>.</li>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3457 <li><tt>static ConstantInt* get(const Type *Ty, uint64_t Val)</tt>:
3458 Returns the ConstantInt object that represents the value provided by
3459 <tt>Val</tt> for integer type <tt>Ty</tt>.</li>
3460 </ul>
3461 </li>
3462 <li>ConstantFP : This class represents a floating point constant.
3463 <ul>
3464 <li><tt>double getValue() const</tt>: Returns the underlying value of
3465 this constant. </li>
3466 </ul>
3467 </li>
3468 <li>ConstantArray : This represents a constant array.
3469 <ul>
3470 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
3471 a vector of component constants that makeup this array. </li>
3472 </ul>
3473 </li>
3474 <li>ConstantStruct : This represents a constant struct.
3475 <ul>
3476 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
3477 a vector of component constants that makeup this array. </li>
3478 </ul>
3479 </li>
3480 <li>GlobalValue : This represents either a global variable or a function. In
3481 either case, the value is a constant fixed address (after linking).
3482 </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3483</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3484</div>
3485
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3486</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3487
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3488<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3489<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3490 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3491</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3492
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3493<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3494
3495<p><tt>#include "<a
3496href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]3497doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
3498Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3499Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
3500<a href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3501
3502<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
3503href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
3504visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
3505Because they are visible at global scope, they are also subject to linking with
3506other globals defined in different translation units. To control the linking
3507process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
3508<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]3509defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3510
3511<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
3512<tt>static</tt> in C), it is not visible to code outside the current translation
3513unit, and does not participate in linking. If it has external linkage, it is
3514visible to external code, and does participate in linking. In addition to
3515linkage information, <tt>GlobalValue</tt>s keep track of which <a
3516href="#Module"><tt>Module</tt></a> they are currently part of.</p>
3517
3518<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
3519by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
3520global is always a pointer to its contents. It is important to remember this
3521when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
3522be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
3523subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]3524i32]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3525the address of the first element of this array and the value of the
3526<tt>GlobalVariable</tt> are the same, they have different types. The
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]3527<tt>GlobalVariable</tt>'s type is <tt>[24 x i32]</tt>. The first element's type
3528is <tt>i32.</tt> Because of this, accessing a global value requires you to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3529dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
3530can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
3531Language Reference Manual</a>.</p>
3532
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3533<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3534<h4>
3535 <a name="m_GlobalValue">
3536 Important Public Members of the <tt>GlobalValue</tt> class
3537 </a>
3538</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3539
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3540<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3541
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3542<ul>
3543 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3544 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3545 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
3546 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
3547 <p> </p>
3548 </li>
3549 <li><tt><a href="#Module">Module</a> *getParent()</tt>
3550 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3551GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3552</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3553
3554</div>
3555
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3556</div>
3557
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3558<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3559<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3560 <a name="Function">The <tt>Function</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3561</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3562
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3563<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3564
3565<p><tt>#include "<a
3566href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]3567info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3568Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
3569<a href="#Constant"><tt>Constant</tt></a>,
3570<a href="#User"><tt>User</tt></a>,
3571<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3572
3573<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
Torok Edwin87469292009-10-12 13:37:29 +0000[diff] [blame]3574actually one of the more complex classes in the LLVM hierarchy because it must
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3575keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3576of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
3577<a href="#Argument"><tt>Argument</tt></a>s, and a
3578<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3579
3580<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
3581commonly used part of <tt>Function</tt> objects. The list imposes an implicit
3582ordering of the blocks in the function, which indicate how the code will be
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3583laid out by the backend. Additionally, the first <a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3584href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
3585<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
3586block. There are no implicit exit nodes, and in fact there may be multiple exit
3587nodes from a single <tt>Function</tt>. If the <a
3588href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
3589the <tt>Function</tt> is actually a function declaration: the actual body of the
3590function hasn't been linked in yet.</p>
3591
3592<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
3593<tt>Function</tt> class also keeps track of the list of formal <a
3594href="#Argument"><tt>Argument</tt></a>s that the function receives. This
3595container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
3596nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
3597the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
3598
3599<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
3600LLVM feature that is only used when you have to look up a value by name. Aside
3601from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
3602internally to make sure that there are not conflicts between the names of <a
3603href="#Instruction"><tt>Instruction</tt></a>s, <a
3604href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
3605href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
3606
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]3607<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
3608and therefore also a <a href="#Constant">Constant</a>. The value of the function
3609is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3610
3611<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3612<h4>
3613 <a name="m_Function">
3614 Important Public Members of the <tt>Function</tt> class
3615 </a>
3616</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3617
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3618<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3619
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3620<ul>
3621 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]3622 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3623
3624 <p>Constructor used when you need to create new <tt>Function</tt>s to add
3625 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]3626 create and what type of linkage the function should have. The <a
3627 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3628 specifies the formal arguments and return value for the function. The same
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]3629 <a href="#FunctionType"><tt>FunctionType</tt></a> value can be used to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3630 create multiple functions. The <tt>Parent</tt> argument specifies the Module
3631 in which the function is defined. If this argument is provided, the function
3632 will automatically be inserted into that module's list of
3633 functions.</p></li>
3634
Chris Lattner62810e32008-11-25 18:34:50 +0000[diff] [blame]3635 <li><tt>bool isDeclaration()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3636
3637 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
3638 function is "external", it does not have a body, and thus must be resolved
3639 by linking with a function defined in a different translation unit.</p></li>
3640
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3641 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3642 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3643
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]3644 <tt>begin()</tt>, <tt>end()</tt>
3645 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3646
3647 <p>These are forwarding methods that make it easy to access the contents of
3648 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
3649 list.</p></li>
3650
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3651 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3652
3653 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
3654 is necessary to use when you need to update the list or perform a complex
3655 action that doesn't have a forwarding method.</p></li>
3656
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]3657 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3658iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]3659 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3660
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]3661 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]3662 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3663
3664 <p>These are forwarding methods that make it easy to access the contents of
3665 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
3666 list.</p></li>
3667
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3668 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3669
3670 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
3671 necessary to use when you need to update the list or perform a complex
3672 action that doesn't have a forwarding method.</p></li>
3673
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3674 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3675
3676 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
3677 function. Because the entry block for the function is always the first
3678 block, this returns the first block of the <tt>Function</tt>.</p></li>
3679
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3680 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
3681 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3682
3683 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
3684 <tt>Function</tt> and returns the return type of the function, or the <a
3685 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
3686 function.</p></li>
3687
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3688 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3689
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3690 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3691 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3692</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3693
3694</div>
3695
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3696</div>
3697
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3698<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3699<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3700 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3701</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3702
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3703<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3704
3705<p><tt>#include "<a
3706href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
3707<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]3708doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3709 Class</a><br>
3710Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
3711<a href="#Constant"><tt>Constant</tt></a>,
3712<a href="#User"><tt>User</tt></a>,
3713<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3714
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3715<p>Global variables are represented with the (surprise surprise)
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3716<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
3717subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
3718always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3719"name" refers to their constant address). See
3720<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
3721variables may have an initial value (which must be a
3722<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
3723they may be marked as "constant" themselves (indicating that their contents
3724never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3725
3726<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3727<h4>
3728 <a name="m_GlobalVariable">
3729 Important Public Members of the <tt>GlobalVariable</tt> class
3730 </a>
3731</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3732
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3733<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3734
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3735<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3736 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
3737 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
3738 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
3739
3740 <p>Create a new global variable of the specified type. If
3741 <tt>isConstant</tt> is true then the global variable will be marked as
3742 unchanging for the program. The Linkage parameter specifies the type of
Duncan Sands667d4b82009-03-07 15:45:40 +0000[diff] [blame]3743 linkage (internal, external, weak, linkonce, appending) for the variable.
3744 If the linkage is InternalLinkage, WeakAnyLinkage, WeakODRLinkage,
3745 LinkOnceAnyLinkage or LinkOnceODRLinkage,&nbsp; then the resultant
3746 global variable will have internal linkage. AppendingLinkage concatenates
3747 together all instances (in different translation units) of the variable
3748 into a single variable but is only applicable to arrays. &nbsp;See
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3749 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
3750 further details on linkage types. Optionally an initializer, a name, and the
3751 module to put the variable into may be specified for the global variable as
3752 well.</p></li>
3753
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3754 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3755
3756 <p>Returns true if this is a global variable that is known not to
3757 be modified at runtime.</p></li>
3758
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3759 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3760
3761 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
3762
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3763 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3764
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3765 <p>Returns the initial value for a <tt>GlobalVariable</tt>. It is not legal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3766 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3767</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3768
3769</div>
3770
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3771</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3772
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3773<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3774<h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3775 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3776</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3777
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3778<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3779
3780<p><tt>#include "<a
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3781href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
Stefanus Du Toit24e04112009-06-17 21:12:26 +0000[diff] [blame]3782doxygen info: <a href="/doxygen/classllvm_1_1BasicBlock.html">BasicBlock
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3783Class</a><br>
3784Superclass: <a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3785
Nick Lewyckyccd279d2011-02-17 02:19:22 +0000[diff] [blame]3786<p>This class represents a single entry single exit section of the code,
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3787commonly known as a basic block by the compiler community. The
3788<tt>BasicBlock</tt> class maintains a list of <a
3789href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
3790Matching the language definition, the last element of this list of instructions
3791is always a terminator instruction (a subclass of the <a
3792href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
3793
3794<p>In addition to tracking the list of instructions that make up the block, the
3795<tt>BasicBlock</tt> class also keeps track of the <a
3796href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
3797
3798<p>Note that <tt>BasicBlock</tt>s themselves are <a
3799href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
3800like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
3801<tt>label</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3802
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3803<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3804<h4>
3805 <a name="m_BasicBlock">
3806 Important Public Members of the <tt>BasicBlock</tt> class
3807 </a>
3808</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3809
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3810<div>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3811<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3812
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3813<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
3814 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3815
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3816<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
3817insertion into a function. The constructor optionally takes a name for the new
3818block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
3819the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
3820automatically inserted at the end of the specified <a
3821href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
3822manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3823
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3824<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
3825<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
3826<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
3827<tt>size()</tt>, <tt>empty()</tt>
3828STL-style functions for accessing the instruction list.
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3829
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3830<p>These methods and typedefs are forwarding functions that have the same
3831semantics as the standard library methods of the same names. These methods
3832expose the underlying instruction list of a basic block in a way that is easy to
3833manipulate. To get the full complement of container operations (including
3834operations to update the list), you must use the <tt>getInstList()</tt>
3835method.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3836
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3837<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3838
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3839<p>This method is used to get access to the underlying container that actually
3840holds the Instructions. This method must be used when there isn't a forwarding
3841function in the <tt>BasicBlock</tt> class for the operation that you would like
3842to perform. Because there are no forwarding functions for "updating"
3843operations, you need to use this if you want to update the contents of a
3844<tt>BasicBlock</tt>.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3845
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3846<li><tt><a href="#Function">Function</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3847
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3848<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
3849embedded into, or a null pointer if it is homeless.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3850
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3851<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3852
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3853<p> Returns a pointer to the terminator instruction that appears at the end of
3854the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
3855instruction in the block is not a terminator, then a null pointer is
3856returned.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3857
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3858</ul>
3859
3860</div>
3861
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3862</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3863
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3864<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3865<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3866 <a name="Argument">The <tt>Argument</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3867</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3868
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3869<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3870
3871<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]3872arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3873arguments. An argument has a pointer to the parent Function.</p>
3874
3875</div>
3876
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3877</div>
3878
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3879<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3880<hr>
3881<address>
3882 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]3883 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3884 <a href="http://validator.w3.org/check/referer"><img
Gabor Greifa9c0f2b2008-06-18 14:05:31 +0000[diff] [blame]3885 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Strict"></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3886
3887 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
3888 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]3889 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3890 Last modified: $Date$
3891</address>
3892
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3893</body>
3894</html>