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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 Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]71 <li><a href="#ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
72 <ul>
73 <li><a href="#dss_sortedvectorset">A sorted 'vector'</a></li>
74 <li><a href="#dss_smallset">"llvm/ADT/SmallSet.h"</a></li>
75 <li><a href="#dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a></li>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]76 <li><a href="#dss_denseset">"llvm/ADT/DenseSet.h"</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]77 <li><a href="#dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a></li>
78 <li><a href="#dss_set">&lt;set&gt;</a></li>
79 <li><a href="#dss_setvector">"llvm/ADT/SetVector.h"</a></li>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]80 <li><a href="#dss_uniquevector">"llvm/ADT/UniqueVector.h"</a></li>
81 <li><a href="#dss_otherset">Other Set-Like ContainerOptions</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]82 </ul></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]83 <li><a href="#ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
84 <ul>
85 <li><a href="#dss_sortedvectormap">A sorted 'vector'</a></li>
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]86 <li><a href="#dss_stringmap">"llvm/ADT/StringMap.h"</a></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]87 <li><a href="#dss_indexedmap">"llvm/ADT/IndexedMap.h"</a></li>
88 <li><a href="#dss_densemap">"llvm/ADT/DenseMap.h"</a></li>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]89 <li><a href="#dss_valuemap">"llvm/ADT/ValueMap.h"</a></li>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]90 <li><a href="#dss_intervalmap">"llvm/ADT/IntervalMap.h"</a></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]91 <li><a href="#dss_map">&lt;map&gt;</a></li>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]92 <li><a href="#dss_inteqclasses">"llvm/ADT/IntEqClasses.h"</a></li>
Chris Lattnerf3692522007-02-03 19:51:56 +0000[diff] [blame]93 <li><a href="#dss_othermap">Other Map-Like Container Options</a></li>
94 </ul></li>
Chris Lattnerdced9fb2009-07-25 07:22:20 +0000[diff] [blame]95 <li><a href="#ds_string">String-like containers</a>
Benjamin Kramere15192b2009-08-05 15:42:44 +0000[diff] [blame]96 <!--<ul>
97 todo
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 Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1217 <a name="ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1218</h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1219
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1220<div>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1221
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1222<p>Set-like containers are useful when you need to canonicalize multiple values
1223into a single representation. There are several different choices for how to do
1224this, providing various trade-offs.</p>
1225
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1226<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1227<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1228 <a name="dss_sortedvectorset">A sorted 'vector'</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1229</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1230
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1231<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1232
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame]1233<p>If you intend to insert a lot of elements, then do a lot of queries, a
1234great approach is to use a vector (or other sequential container) with
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1235std::sort+std::unique to remove duplicates. This approach works really well if
Chris Lattner3b23a8c2007-02-03 08:10:45 +0000[diff] [blame]1236your usage pattern has these two distinct phases (insert then query), and can be
1237coupled with a good choice of <a href="#ds_sequential">sequential container</a>.
1238</p>
1239
1240<p>
1241This combination provides the several nice properties: the result data is
1242contiguous in memory (good for cache locality), has few allocations, is easy to
1243address (iterators in the final vector are just indices or pointers), and can be
1244efficiently queried with a standard binary or radix search.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1245
1246</div>
1247
1248<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1249<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1250 <a name="dss_smallset">"llvm/ADT/SmallSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1251</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1252
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1253<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1254
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1255<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]1256are 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]1257has space for N elements in place (thus, if the set is dynamically smaller than
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1258N, no malloc traffic is required) and accesses them with a simple linear search.
1259When the set grows beyond 'N' elements, it allocates a more expensive representation that
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1260guarantees efficient access (for most types, it falls back to std::set, but for
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1261pointers it uses something far better, <a
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1262href="#dss_smallptrset">SmallPtrSet</a>).</p>
1263
1264<p>The magic of this class is that it handles small sets extremely efficiently,
1265but gracefully handles extremely large sets without loss of efficiency. The
1266drawback is that the interface is quite small: it supports insertion, queries
1267and erasing, but does not support iteration.</p>
1268
1269</div>
1270
1271<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1272<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1273 <a name="dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1274</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1275
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1276<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1277
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]1278<p>SmallPtrSet has all the advantages of <tt>SmallSet</tt> (and a <tt>SmallSet</tt> of pointers is
1279transparently implemented with a <tt>SmallPtrSet</tt>), but also supports iterators. If
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1280more than 'N' insertions are performed, a single quadratically
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1281probed hash table is allocated and grows as needed, providing extremely
1282efficient access (constant time insertion/deleting/queries with low constant
1283factors) and is very stingy with malloc traffic.</p>
1284
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]1285<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]1286whenever an insertion occurs. Also, the values visited by the iterators are not
1287visited in sorted order.</p>
1288
1289</div>
1290
1291<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1292<h4>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]1293 <a name="dss_denseset">"llvm/ADT/DenseSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1294</h4>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]1295
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1296<div>
Chris Lattnerc28476f2007-09-30 00:58:59 +0000[diff] [blame]1297
1298<p>
1299DenseSet is a simple quadratically probed hash table. It excels at supporting
1300small values: it uses a single allocation to hold all of the pairs that
1301are currently inserted in the set. DenseSet is a great way to unique small
1302values that are not simple pointers (use <a
1303href="#dss_smallptrset">SmallPtrSet</a> for pointers). Note that DenseSet has
1304the same requirements for the value type that <a
1305href="#dss_densemap">DenseMap</a> has.
1306</p>
1307
1308</div>
1309
1310<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1311<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1312 <a name="dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1313</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1314
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1315<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1316
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1317<p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1318FoldingSet is an aggregate class that is really good at uniquing
1319expensive-to-create or polymorphic objects. It is a combination of a chained
1320hash table with intrusive links (uniqued objects are required to inherit from
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1321FoldingSetNode) that uses <a href="#dss_smallvector">SmallVector</a> as part of
1322its ID process.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1323
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1324<p>Consider a case where you want to implement a "getOrCreateFoo" method for
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1325a complex object (for example, a node in the code generator). The client has a
1326description of *what* it wants to generate (it knows the opcode and all the
1327operands), 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]1328only to find out it already exists, at which point we would have to delete it
1329and return the node that already exists.
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1330</p>
1331
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1332<p>To support this style of client, FoldingSet perform a query with a
1333FoldingSetNodeID (which wraps SmallVector) that can be used to describe the
1334element that we want to query for. The query either returns the element
1335matching the ID or it returns an opaque ID that indicates where insertion should
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1336take place. Construction of the ID usually does not require heap traffic.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1337
1338<p>Because FoldingSet uses intrusive links, it can support polymorphic objects
1339in the set (for example, you can have SDNode instances mixed with LoadSDNodes).
1340Because the elements are individually allocated, pointers to the elements are
1341stable: inserting or removing elements does not invalidate any pointers to other
1342elements.
1343</p>
1344
1345</div>
1346
1347<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1348<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1349 <a name="dss_set">&lt;set&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1350</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1351
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1352<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1353
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1354<p><tt>std::set</tt> is a reasonable all-around set class, which is decent at
1355many things but great at nothing. std::set allocates memory for each element
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1356inserted (thus it is very malloc intensive) and typically stores three pointers
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1357per element in the set (thus adding a large amount of per-element space
1358overhead). It offers guaranteed log(n) performance, which is not particularly
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1359fast from a complexity standpoint (particularly if the elements of the set are
1360expensive to compare, like strings), and has extremely high constant factors for
1361lookup, insertion and removal.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1362
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1363<p>The advantages of std::set are that its iterators are stable (deleting or
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1364inserting an element from the set does not affect iterators or pointers to other
1365elements) and that iteration over the set is guaranteed to be in sorted order.
1366If the elements in the set are large, then the relative overhead of the pointers
1367and malloc traffic is not a big deal, but if the elements of the set are small,
1368std::set is almost never a good choice.</p>
1369
1370</div>
1371
1372<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1373<h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1374 <a name="dss_setvector">"llvm/ADT/SetVector.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1375</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1376
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1377<div>
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1378<p>LLVM's SetVector&lt;Type&gt; is an adapter class that combines your choice of
1379a set-like container along with a <a href="#ds_sequential">Sequential
1380Container</a>. The important property
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1381that this provides is efficient insertion with uniquing (duplicate elements are
1382ignored) with iteration support. It implements this by inserting elements into
1383both a set-like container and the sequential container, using the set-like
1384container for uniquing and the sequential container for iteration.
1385</p>
1386
1387<p>The difference between SetVector and other sets is that the order of
1388iteration is guaranteed to match the order of insertion into the SetVector.
1389This property is really important for things like sets of pointers. Because
1390pointer values are non-deterministic (e.g. vary across runs of the program on
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1391different machines), iterating over the pointers in the set will
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1392not be in a well-defined order.</p>
1393
1394<p>
1395The drawback of SetVector is that it requires twice as much space as a normal
1396set and has the sum of constant factors from the set-like container and the
1397sequential container that it uses. Use it *only* if you need to iterate over
1398the elements in a deterministic order. SetVector is also expensive to delete
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1399elements out of (linear time), unless you use it's "pop_back" method, which is
1400faster.
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1401</p>
1402
Chris Lattneredca3c52007-02-04 00:00:26 +0000[diff] [blame]1403<p>SetVector is an adapter class that defaults to using std::vector and std::set
1404for the underlying containers, so it is quite expensive. However,
1405<tt>"llvm/ADT/SetVector.h"</tt> also provides a SmallSetVector class, which
1406defaults to using a SmallVector and SmallSet of a specified size. If you use
1407this, and if your sets are dynamically smaller than N, you will save a lot of
1408heap traffic.</p>
1409
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1410</div>
1411
1412<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1413<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1414 <a name="dss_uniquevector">"llvm/ADT/UniqueVector.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1415</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1416
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1417<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1418
1419<p>
1420UniqueVector is similar to <a href="#dss_setvector">SetVector</a>, but it
1421retains a unique ID for each element inserted into the set. It internally
1422contains a map and a vector, and it assigns a unique ID for each value inserted
1423into the set.</p>
1424
1425<p>UniqueVector is very expensive: its cost is the sum of the cost of
1426maintaining both the map and vector, it has high complexity, high constant
1427factors, and produces a lot of malloc traffic. It should be avoided.</p>
1428
1429</div>
1430
1431
1432<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1433<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1434 <a name="dss_otherset">Other Set-Like Container Options</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1435</h4>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1436
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1437<div>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1438
1439<p>
1440The STL provides several other options, such as std::multiset and the various
Chris Lattnerf1a30822009-03-09 05:20:45 +0000[diff] [blame]1441"hash_set" like containers (whether from C++ TR1 or from the SGI library). We
1442never use hash_set and unordered_set because they are generally very expensive
1443(each insertion requires a malloc) and very non-portable.
1444</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1445
1446<p>std::multiset is useful if you're not interested in elimination of
Chris Lattner14868db2007-02-03 08:20:15 +0000[diff] [blame]1447duplicates, but has all the drawbacks of std::set. A sorted vector (where you
1448don't delete duplicate entries) or some other approach is almost always
1449better.</p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame]1450
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1451</div>
1452
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1453</div>
1454
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1455<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1456<h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1457 <a name="ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1458</h3>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1459
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1460<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1461Map-like containers are useful when you want to associate data to a key. As
1462usual, there are a lot of different ways to do this. :)
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1463
1464<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1465<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1466 <a name="dss_sortedvectormap">A sorted 'vector'</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1467</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1468
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1469<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1470
1471<p>
1472If your usage pattern follows a strict insert-then-query approach, you can
1473trivially use the same approach as <a href="#dss_sortedvectorset">sorted vectors
1474for set-like containers</a>. The only difference is that your query function
1475(which uses std::lower_bound to get efficient log(n) lookup) should only compare
1476the key, not both the key and value. This yields the same advantages as sorted
1477vectors for sets.
1478</p>
1479</div>
1480
1481<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1482<h4>
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1483 <a name="dss_stringmap">"llvm/ADT/StringMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1484</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1485
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1486<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1487
1488<p>
1489Strings are commonly used as keys in maps, and they are difficult to support
1490efficiently: they are variable length, inefficient to hash and compare when
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1491long, expensive to copy, etc. StringMap is a specialized container designed to
1492cope with these issues. It supports mapping an arbitrary range of bytes to an
1493arbitrary other object.</p>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1494
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1495<p>The StringMap implementation uses a quadratically-probed hash table, where
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1496the buckets store a pointer to the heap allocated entries (and some other
1497stuff). The entries in the map must be heap allocated because the strings are
1498variable length. The string data (key) and the element object (value) are
1499stored in the same allocation with the string data immediately after the element
1500object. This container guarantees the "<tt>(char*)(&amp;Value+1)</tt>" points
1501to the key string for a value.</p>
1502
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1503<p>The StringMap is very fast for several reasons: quadratic probing is very
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1504cache efficient for lookups, the hash value of strings in buckets is not
Nick Lewycky2a80aca2010-08-01 23:18:45 +0000[diff] [blame]1505recomputed when looking up an element, StringMap rarely has to touch the
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1506memory for unrelated objects when looking up a value (even when hash collisions
1507happen), hash table growth does not recompute the hash values for strings
1508already in the table, and each pair in the map is store in a single allocation
1509(the string data is stored in the same allocation as the Value of a pair).</p>
1510
Chris Lattner796f9fa2007-02-08 19:14:21 +0000[diff] [blame]1511<p>StringMap also provides query methods that take byte ranges, so it only ever
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1512copies a string if a value is inserted into the table.</p>
1513</div>
1514
1515<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1516<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1517 <a name="dss_indexedmap">"llvm/ADT/IndexedMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1518</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1519
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1520<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1521<p>
1522IndexedMap is a specialized container for mapping small dense integers (or
1523values that can be mapped to small dense integers) to some other type. It is
1524internally implemented as a vector with a mapping function that maps the keys to
1525the dense integer range.
1526</p>
1527
1528<p>
1529This is useful for cases like virtual registers in the LLVM code generator: they
1530have a dense mapping that is offset by a compile-time constant (the first
1531virtual register ID).</p>
1532
1533</div>
1534
1535<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1536<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1537 <a name="dss_densemap">"llvm/ADT/DenseMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1538</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1539
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1540<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1541
1542<p>
1543DenseMap is a simple quadratically probed hash table. It excels at supporting
1544small keys and values: it uses a single allocation to hold all of the pairs that
1545are currently inserted in the map. DenseMap is a great way to map pointers to
1546pointers, or map other small types to each other.
1547</p>
1548
1549<p>
1550There are several aspects of DenseMap that you should be aware of, however. The
1551iterators in a densemap are invalidated whenever an insertion occurs, unlike
1552map. Also, because DenseMap allocates space for a large number of key/value
Chris Lattnera4a264d2007-02-03 20:17:53 +0000[diff] [blame]1553pairs (it starts with 64 by default), it will waste a lot of space if your keys
1554or values are large. Finally, you must implement a partial specialization of
Chris Lattner76c1b972007-09-17 18:34:04 +0000[diff] [blame]1555DenseMapInfo for the key that you want, if it isn't already supported. This
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1556is required to tell DenseMap about two special marker values (which can never be
Chris Lattnera4a264d2007-02-03 20:17:53 +0000[diff] [blame]1557inserted into the map) that it needs internally.</p>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1558
1559</div>
1560
1561<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1562<h4>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]1563 <a name="dss_valuemap">"llvm/ADT/ValueMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1564</h4>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]1565
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1566<div>
Jeffrey Yasskin71a5c222009-10-22 22:11:22 +0000[diff] [blame]1567
1568<p>
1569ValueMap is a wrapper around a <a href="#dss_densemap">DenseMap</a> mapping
1570Value*s (or subclasses) to another type. When a Value is deleted or RAUW'ed,
1571ValueMap will update itself so the new version of the key is mapped to the same
1572value, just as if the key were a WeakVH. You can configure exactly how this
1573happens, and what else happens on these two events, by passing
1574a <code>Config</code> parameter to the ValueMap template.</p>
1575
1576</div>
1577
1578<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1579<h4>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]1580 <a name="dss_intervalmap">"llvm/ADT/IntervalMap.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1581</h4>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]1582
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1583<div>
Jakob Stoklund Olesenaca0da62010-12-14 00:55:51 +0000[diff] [blame]1584
1585<p> IntervalMap is a compact map for small keys and values. It maps key
1586intervals instead of single keys, and it will automatically coalesce adjacent
1587intervals. When then map only contains a few intervals, they are stored in the
1588map object itself to avoid allocations.</p>
1589
1590<p> The IntervalMap iterators are quite big, so they should not be passed around
1591as STL iterators. The heavyweight iterators allow a smaller data structure.</p>
1592
1593</div>
1594
1595<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1596<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1597 <a name="dss_map">&lt;map&gt;</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1598</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1599
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1600<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1601
1602<p>
1603std::map has similar characteristics to <a href="#dss_set">std::set</a>: it uses
1604a single allocation per pair inserted into the map, it offers log(n) lookup with
1605an extremely large constant factor, imposes a space penalty of 3 pointers per
1606pair in the map, etc.</p>
1607
1608<p>std::map is most useful when your keys or values are very large, if you need
1609to iterate over the collection in sorted order, or if you need stable iterators
1610into the map (i.e. they don't get invalidated if an insertion or deletion of
1611another element takes place).</p>
1612
1613</div>
1614
1615<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1616<h4>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]1617 <a name="dss_inteqclasses">"llvm/ADT/IntEqClasses.h"</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1618</h4>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]1619
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1620<div>
Jakob Stoklund Olesen4359e5e2011-04-05 20:56:08 +0000[diff] [blame]1621
1622<p>IntEqClasses provides a compact representation of equivalence classes of
1623small integers. Initially, each integer in the range 0..n-1 has its own
1624equivalence class. Classes can be joined by passing two class representatives to
1625the join(a, b) method. Two integers are in the same class when findLeader()
1626returns the same representative.</p>
1627
1628<p>Once all equivalence classes are formed, the map can be compressed so each
1629integer 0..n-1 maps to an equivalence class number in the range 0..m-1, where m
1630is the total number of equivalence classes. The map must be uncompressed before
1631it can be edited again.</p>
1632
1633</div>
1634
1635<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1636<h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1637 <a name="dss_othermap">Other Map-Like Container Options</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1638</h4>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1639
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1640<div>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1641
1642<p>
1643The STL provides several other options, such as std::multimap and the various
Chris Lattnerf1a30822009-03-09 05:20:45 +0000[diff] [blame]1644"hash_map" like containers (whether from C++ TR1 or from the SGI library). We
1645never use hash_set and unordered_set because they are generally very expensive
1646(each insertion requires a malloc) and very non-portable.</p>
Chris Lattnerc5722432007-02-03 19:49:31 +0000[diff] [blame]1647
1648<p>std::multimap is useful if you want to map a key to multiple values, but has
1649all the drawbacks of std::map. A sorted vector or some other approach is almost
1650always better.</p>
1651
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1652</div>
1653
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1654</div>
1655
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1656<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1657<h3>
Chris Lattnerdced9fb2009-07-25 07:22:20 +0000[diff] [blame]1658 <a name="ds_string">String-like containers</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1659</h3>
Chris Lattnerdced9fb2009-07-25 07:22:20 +0000[diff] [blame]1660
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1661<div>
Chris Lattnerdced9fb2009-07-25 07:22:20 +0000[diff] [blame]1662
1663<p>
1664TODO: const char* vs stringref vs smallstring vs std::string. Describe twine,
1665xref to #string_apis.
1666</p>
1667
1668</div>
1669
1670<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1671<h3>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1672 <a name="ds_bit">Bit storage containers (BitVector, SparseBitVector)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1673</h3>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1674
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1675<div>
Chris Lattner7086ce72007-09-25 22:37:50 +0000[diff] [blame]1676<p>Unlike the other containers, there are only two bit storage containers, and
1677choosing when to use each is relatively straightforward.</p>
1678
1679<p>One additional option is
1680<tt>std::vector&lt;bool&gt;</tt>: we discourage its use for two reasons 1) the
1681implementation in many common compilers (e.g. commonly available versions of
1682GCC) is extremely inefficient and 2) the C++ standards committee is likely to
1683deprecate this container and/or change it significantly somehow. In any case,
1684please don't use it.</p>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1685
1686<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1687<h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1688 <a name="dss_bitvector">BitVector</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1689</h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1690
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1691<div>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1692<p> The BitVector container provides a dynamic size set of bits for manipulation.
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1693It supports individual bit setting/testing, as well as set operations. The set
1694operations take time O(size of bitvector), but operations are performed one word
1695at a time, instead of one bit at a time. This makes the BitVector very fast for
1696set operations compared to other containers. Use the BitVector when you expect
1697the number of set bits to be high (IE a dense set).
1698</p>
1699</div>
1700
1701<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1702<h4>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1703 <a name="dss_smallbitvector">SmallBitVector</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1704</h4>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1705
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1706<div>
Dan Gohman5f7775c2010-01-05 18:24:00 +0000[diff] [blame]1707<p> The SmallBitVector container provides the same interface as BitVector, but
1708it is optimized for the case where only a small number of bits, less than
170925 or so, are needed. It also transparently supports larger bit counts, but
1710slightly less efficiently than a plain BitVector, so SmallBitVector should
1711only be used when larger counts are rare.
1712</p>
1713
1714<p>
1715At this time, SmallBitVector does not support set operations (and, or, xor),
1716and its operator[] does not provide an assignable lvalue.
1717</p>
1718</div>
1719
1720<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1721<h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1722 <a name="dss_sparsebitvector">SparseBitVector</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1723</h4>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1724
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1725<div>
Daniel Berlin1939ace2007-09-24 17:52:25 +0000[diff] [blame]1726<p> The SparseBitVector container is much like BitVector, with one major
1727difference: Only the bits that are set, are stored. This makes the
1728SparseBitVector much more space efficient than BitVector when the set is sparse,
1729as well as making set operations O(number of set bits) instead of O(size of
1730universe). 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
1731(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).
1732</p>
1733</div>
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]1734
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1735</div>
1736
1737</div>
1738
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1739<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1740<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1741 <a name="common">Helpful Hints for Common Operations</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1742</h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1743<!-- *********************************************************************** -->
1744
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1745<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1746
1747<p>This section describes how to perform some very simple transformations of
1748LLVM code. This is meant to give examples of common idioms used, showing the
1749practical side of LLVM transformations. <p> Because this is a "how-to" section,
1750you should also read about the main classes that you will be working with. The
1751<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
1752and descriptions of the main classes that you should know about.</p>
1753
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1754<!-- NOTE: this section should be heavy on example code -->
1755<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1756<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1757 <a name="inspection">Basic Inspection and Traversal Routines</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1758</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1759
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1760<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1761
1762<p>The LLVM compiler infrastructure have many different data structures that may
1763be traversed. Following the example of the C++ standard template library, the
1764techniques used to traverse these various data structures are all basically the
1765same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
1766method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
1767function returns an iterator pointing to one past the last valid element of the
1768sequence, and there is some <tt>XXXiterator</tt> data type that is common
1769between the two operations.</p>
1770
1771<p>Because the pattern for iteration is common across many different aspects of
1772the program representation, the standard template library algorithms may be used
1773on them, and it is easier to remember how to iterate. First we show a few common
1774examples of the data structures that need to be traversed. Other data
1775structures are traversed in very similar ways.</p>
1776
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1777<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1778<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1779 <a name="iterate_function">Iterating over the </a><a
1780 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
1781 href="#Function"><tt>Function</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1782</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1783
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1784<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1785
1786<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
1787transform in some way; in particular, you'd like to manipulate its
1788<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
1789the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
1790an example that prints the name of a <tt>BasicBlock</tt> and the number of
1791<tt>Instruction</tt>s it contains:</p>
1792
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1793<div class="doc_code">
1794<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1795// <i>func is a pointer to a Function instance</i>
1796for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i)
1797 // <i>Print out the name of the basic block if it has one, and then the</i>
1798 // <i>number of instructions that it contains</i>
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1799 errs() &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has "
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1800 &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1801</pre>
1802</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1803
1804<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]1805invoking member functions of the <tt>Instruction</tt> class. This is
1806because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]1807classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1808exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
1809
1810</div>
1811
1812<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1813<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1814 <a name="iterate_basicblock">Iterating over the </a><a
1815 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1816 href="#BasicBlock"><tt>BasicBlock</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1817</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1818
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1819<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1820
1821<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
1822easy to iterate over the individual instructions that make up
1823<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
1824a <tt>BasicBlock</tt>:</p>
1825
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1826<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1827<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1828// <i>blk is a pointer to a BasicBlock instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1829for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1830 // <i>The next statement works since operator&lt;&lt;(ostream&amp;,...)</i>
1831 // <i>is overloaded for Instruction&amp;</i>
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1832 errs() &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1833</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1834</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1835
1836<p>However, this isn't really the best way to print out the contents of a
1837<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
1838anything you'll care about, you could have just invoked the print routine on the
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1839basic block itself: <tt>errs() &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1840
1841</div>
1842
1843<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1844<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1845 <a name="iterate_institer">Iterating over the </a><a
1846 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1847 href="#Function"><tt>Function</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1848</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1849
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1850<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1851
1852<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
1853<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
1854<tt>InstIterator</tt> should be used instead. You'll need to include <a
1855href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
1856and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1857small 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]1858
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1859<div class="doc_code">
1860<pre>
1861#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
1862
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1863// <i>F is a pointer to a Function instance</i>
Chris Lattnerda021aa2008-06-04 18:20:42 +0000[diff] [blame]1864for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1865 errs() &lt;&lt; *I &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1866</pre>
1867</div>
1868
1869<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]1870work list with its initial contents. For example, if you wanted to
1871initialize a work list to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1872F, all you would need to do is something like:</p>
1873
1874<div class="doc_code">
1875<pre>
1876std::set&lt;Instruction*&gt; worklist;
Chris Lattnerda021aa2008-06-04 18:20:42 +0000[diff] [blame]1877// or better yet, SmallPtrSet&lt;Instruction*, 64&gt; worklist;
1878
1879for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
1880 worklist.insert(&amp;*I);
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1881</pre>
1882</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1883
1884<p>The STL set <tt>worklist</tt> would now contain all instructions in the
1885<tt>Function</tt> pointed to by F.</p>
1886
1887</div>
1888
1889<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1890<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1891 <a name="iterate_convert">Turning an iterator into a class pointer (and
1892 vice-versa)</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1893</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1894
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1895<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1896
1897<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]1898instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1899a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1900Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1901is a <tt>BasicBlock::const_iterator</tt>:</p>
1902
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1903<div class="doc_code">
1904<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1905Instruction&amp; inst = *i; // <i>Grab reference to instruction reference</i>
1906Instruction* pinst = &amp;*i; // <i>Grab pointer to instruction reference</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1907const Instruction&amp; inst = *j;
1908</pre>
1909</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1910
1911<p>However, the iterators you'll be working with in the LLVM framework are
1912special: they will automatically convert to a ptr-to-instance type whenever they
1913need to. Instead of dereferencing the iterator and then taking the address of
1914the result, you can simply assign the iterator to the proper pointer type and
1915you get the dereference and address-of operation as a result of the assignment
1916(behind the scenes, this is a result of overloading casting mechanisms). Thus
1917the last line of the last example,</p>
1918
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1919<div class="doc_code">
1920<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]1921Instruction *pinst = &amp;*i;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1922</pre>
1923</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1924
1925<p>is semantically equivalent to</p>
1926
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1927<div class="doc_code">
1928<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]1929Instruction *pinst = i;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1930</pre>
1931</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1932
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1933<p>It's also possible to turn a class pointer into the corresponding iterator,
1934and this is a constant time operation (very efficient). The following code
1935snippet illustrates use of the conversion constructors provided by LLVM
1936iterators. By using these, you can explicitly grab the iterator of something
1937without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1938
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1939<div class="doc_code">
1940<pre>
1941void printNextInstruction(Instruction* inst) {
1942 BasicBlock::iterator it(inst);
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1943 ++it; // <i>After this line, it refers to the instruction after *inst</i>
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]1944 if (it != inst-&gt;getParent()-&gt;end()) errs() &lt;&lt; *it &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1945}
1946</pre>
1947</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1948
Dan Gohman525bf8e2010-03-26 19:39:05 +0000[diff] [blame]1949<p>Unfortunately, these implicit conversions come at a cost; they prevent
1950these iterators from conforming to standard iterator conventions, and thus
Dan Gohman0d91c112010-03-26 19:51:14 +0000[diff] [blame]1951from being usable with standard algorithms and containers. For example, they
1952prevent the following code, where <tt>B</tt> is a <tt>BasicBlock</tt>,
Dan Gohman525bf8e2010-03-26 19:39:05 +0000[diff] [blame]1953from compiling:</p>
1954
1955<div class="doc_code">
1956<pre>
1957 llvm::SmallVector&lt;llvm::Instruction *, 16&gt;(B-&gt;begin(), B-&gt;end());
1958</pre>
1959</div>
1960
1961<p>Because of this, these implicit conversions may be removed some day,
Dan Gohman0d91c112010-03-26 19:51:14 +0000[diff] [blame]1962and <tt>operator*</tt> changed to return a pointer instead of a reference.</p>
Dan Gohman525bf8e2010-03-26 19:39:05 +0000[diff] [blame]1963
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1964</div>
1965
1966<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1967<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1968 <a name="iterate_complex">Finding call sites: a slightly more complex
1969 example</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]1970</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1971
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]1972<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1973
1974<p>Say that you're writing a FunctionPass and would like to count all the
1975locations in the entire module (that is, across every <tt>Function</tt>) where a
1976certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
1977learn 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]1978much more straight-forward manner, but this example will allow us to explore how
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]1979you'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]1980is what we want to do:</p>
1981
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1982<div class="doc_code">
1983<pre>
1984initialize callCounter to zero
1985for each Function f in the Module
1986 for each BasicBlock b in f
1987 for each Instruction i in b
1988 if (i is a CallInst and calls the given function)
1989 increment callCounter
1990</pre>
1991</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1992
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1993<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1994<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1995override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1996
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1997<div class="doc_code">
1998<pre>
1999Function* targetFunc = ...;
2000
2001class OurFunctionPass : public FunctionPass {
2002 public:
2003 OurFunctionPass(): callCounter(0) { }
2004
2005 virtual runOnFunction(Function&amp; F) {
2006 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
Eric Christopher203e71d2008-11-08 08:20:49 +0000[diff] [blame]2007 for (BasicBlock::iterator i = b-&gt;begin(), ie = b-&gt;end(); i != ie; ++i) {
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2008 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
2009 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2010 // <i>We know we've encountered a call instruction, so we</i>
2011 // <i>need to determine if it's a call to the</i>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2012 // <i>function pointed to by m_func or not.</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2013 if (callInst-&gt;getCalledFunction() == targetFunc)
2014 ++callCounter;
2015 }
2016 }
2017 }
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2018 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2019
2020 private:
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2021 unsigned callCounter;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2022};
2023</pre>
2024</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2025
2026</div>
2027
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]2028<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2029<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2030 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2031</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2032
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2033<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2034
2035<p>You may have noticed that the previous example was a bit oversimplified in
2036that it did not deal with call sites generated by 'invoke' instructions. In
2037this, and in other situations, you may find that you want to treat
2038<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
2039most-specific common base class is <tt>Instruction</tt>, which includes lots of
2040less closely-related things. For these cases, LLVM provides a handy wrapper
2041class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2042href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2043It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
2044methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2045<tt>InvokeInst</tt>s.</p>
2046
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2047<p>This class has "value semantics": it should be passed by value, not by
2048reference and it should not be dynamically allocated or deallocated using
2049<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
2050assignable and constructable, with costs equivalents to that of a bare pointer.
2051If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2052
2053</div>
2054
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]2055<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2056<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2057 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2058</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2059
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2060<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2061
2062<p>Frequently, we might have an instance of the <a
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]2063href="/doxygen/classllvm_1_1Value.html">Value Class</a> and we want to
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2064determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
2065<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
2066For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
2067particular function <tt>foo</tt>. Finding all of the instructions that
2068<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
2069of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2070
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2071<div class="doc_code">
2072<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2073Function *F = ...;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2074
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2075for (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]2076 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
Chris Lattner3fee6ed2009-09-08 05:15:50 +0000[diff] [blame]2077 errs() &lt;&lt; "F is used in instruction:\n";
2078 errs() &lt;&lt; *Inst &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2079 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2080</pre>
Gabor Greif394fdfb2010-03-26 19:35:48 +0000[diff] [blame]2081</div>
2082
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2083<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]2084operation. Instead of performing <tt>*i</tt> above several times, consider
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2085doing it only once in the loop body and reusing its result.</p>
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2086
Gabor Greif6091ff32010-03-26 19:04:42 +0000[diff] [blame]2087<p>Alternatively, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2088href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2089<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
2090<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
2091<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
2092all of the values that a particular instruction uses (that is, the operands of
2093the particular <tt>Instruction</tt>):</p>
2094
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2095<div class="doc_code">
2096<pre>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2097Instruction *pi = ...;
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2098
2099for (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]2100 Value *v = *i;
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2101 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2102}
2103</pre>
2104</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2105
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2106<p>Declaring objects as <tt>const</tt> is an important tool of enforcing
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2107mutation free algorithms (such as analyses, etc.). For this purpose above
Gabor Greif4de73682010-03-26 19:30:47 +0000[diff] [blame]2108iterators come in constant flavors as <tt>Value::const_use_iterator</tt>
2109and <tt>Value::const_op_iterator</tt>. They automatically arise when
2110calling <tt>use/op_begin()</tt> on <tt>const Value*</tt>s or
2111<tt>const User*</tt>s respectively. Upon dereferencing, they return
Gabor Greifce94319532010-03-26 19:40:38 +0000[diff] [blame]2112<tt>const Use*</tt>s. Otherwise the above patterns remain unchanged.</p>
2113
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2114</div>
2115
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2116<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2117<h4>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2118 <a name="iterate_preds">Iterating over predecessors &amp;
2119successors of blocks</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2120</h4>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2121
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2122<div>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2123
2124<p>Iterating over the predecessors and successors of a block is quite easy
2125with the routines defined in <tt>"llvm/Support/CFG.h"</tt>. Just use code like
2126this to iterate over all predecessors of BB:</p>
2127
2128<div class="doc_code">
2129<pre>
2130#include "llvm/Support/CFG.h"
2131BasicBlock *BB = ...;
2132
2133for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
2134 BasicBlock *Pred = *PI;
2135 // <i>...</i>
2136}
2137</pre>
2138</div>
2139
2140<p>Similarly, to iterate over successors use
2141succ_iterator/succ_begin/succ_end.</p>
2142
2143</div>
2144
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2145</div>
Chris Lattner2e438ca2008-01-03 16:56:04 +0000[diff] [blame]2146
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2147<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2148<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2149 <a name="simplechanges">Making simple changes</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2150</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2151
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2152<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2153
2154<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]2155infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2156transformations, it's fairly common to manipulate the contents of basic
2157blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2158and gives example code.</p>
2159
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2160<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2161<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2162 <a name="schanges_creating">Creating and inserting new
2163 <tt>Instruction</tt>s</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2164</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2165
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2166<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2167
2168<p><i>Instantiating Instructions</i></p>
2169
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]2170<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2171constructor for the kind of instruction to instantiate and provide the necessary
2172parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
2173(const-ptr-to) <tt>Type</tt>. Thus:</p>
2174
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2175<div class="doc_code">
2176<pre>
Nick Lewycky10d64b92007-12-03 01:52:52 +0000[diff] [blame]2177AllocaInst* ai = new AllocaInst(Type::Int32Ty);
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2178</pre>
2179</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2180
2181<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]2182one integer in the current stack frame, at run time. Each <tt>Instruction</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2183subclass is likely to have varying default parameters which change the semantics
2184of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2185href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2186Instruction</a> that you're interested in instantiating.</p>
2187
2188<p><i>Naming values</i></p>
2189
2190<p>It is very useful to name the values of instructions when you're able to, as
2191this facilitates the debugging of your transformations. If you end up looking
2192at generated LLVM machine code, you definitely want to have logical names
2193associated with the results of instructions! By supplying a value for the
2194<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
2195associate a logical name with the result of the instruction's execution at
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]2196run time. For example, say that I'm writing a transformation that dynamically
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2197allocates space for an integer on the stack, and that integer is going to be
2198used as some kind of index by some other code. To accomplish this, I place an
2199<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
2200<tt>Function</tt>, and I'm intending to use it within the same
2201<tt>Function</tt>. I might do:</p>
2202
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2203<div class="doc_code">
2204<pre>
Nick Lewycky10d64b92007-12-03 01:52:52 +0000[diff] [blame]2205AllocaInst* pa = new AllocaInst(Type::Int32Ty, 0, "indexLoc");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2206</pre>
2207</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2208
2209<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
Reid Spencer128a7a72007-02-03 21:06:43 +0000[diff] [blame]2210execution value, which is a pointer to an integer on the run time stack.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2211
2212<p><i>Inserting instructions</i></p>
2213
2214<p>There are essentially two ways to insert an <tt>Instruction</tt>
2215into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
2216
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]2217<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2218 <li>Insertion into an explicit instruction list
2219
2220 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
2221 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
2222 before <tt>*pi</tt>, we do the following: </p>
2223
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2224<div class="doc_code">
2225<pre>
2226BasicBlock *pb = ...;
2227Instruction *pi = ...;
2228Instruction *newInst = new Instruction(...);
2229
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2230pb-&gt;getInstList().insert(pi, newInst); // <i>Inserts newInst before pi in pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2231</pre>
2232</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]2233
2234 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
2235 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
2236 classes provide constructors which take a pointer to a
2237 <tt>BasicBlock</tt> to be appended to. For example code that
2238 looked like: </p>
2239
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2240<div class="doc_code">
2241<pre>
2242BasicBlock *pb = ...;
2243Instruction *newInst = new Instruction(...);
2244
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]2245pb-&gt;getInstList().push_back(newInst); // <i>Appends newInst to pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2246</pre>
2247</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]2248
2249 <p>becomes: </p>
2250
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2251<div class="doc_code">
2252<pre>
2253BasicBlock *pb = ...;
2254Instruction *newInst = new Instruction(..., pb);
2255</pre>
2256</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]2257
2258 <p>which is much cleaner, especially if you are creating
2259 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2260
2261 <li>Insertion into an implicit instruction list
2262
2263 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
2264 are implicitly associated with an existing instruction list: the instruction
2265 list of the enclosing basic block. Thus, we could have accomplished the same
2266 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
2267 </p>
2268
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2269<div class="doc_code">
2270<pre>
2271Instruction *pi = ...;
2272Instruction *newInst = new Instruction(...);
2273
2274pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);
2275</pre>
2276</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2277
2278 <p>In fact, this sequence of steps occurs so frequently that the
2279 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
2280 constructors which take (as a default parameter) a pointer to an
2281 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
2282 precede. That is, <tt>Instruction</tt> constructors are capable of
2283 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
2284 provided instruction, immediately before that instruction. Using an
2285 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
2286 parameter, the above code becomes:</p>
2287
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2288<div class="doc_code">
2289<pre>
2290Instruction* pi = ...;
2291Instruction* newInst = new Instruction(..., pi);
2292</pre>
2293</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2294
2295 <p>which is much cleaner, especially if you're creating a lot of
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2296 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2297</ul>
2298
2299</div>
2300
2301<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2302<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2303 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2304</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2305
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2306<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2307
2308<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner49e0ccf2011-03-24 16:13:31 +0000[diff] [blame]2309<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward: just
2310call the instruction's eraseFromParent() method. For example:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2311
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2312<div class="doc_code">
2313<pre>
2314<a href="#Instruction">Instruction</a> *I = .. ;
Chris Lattner9f8ec252008-02-15 22:57:17 +0000[diff] [blame]2315I-&gt;eraseFromParent();
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2316</pre>
2317</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2318
Chris Lattner49e0ccf2011-03-24 16:13:31 +0000[diff] [blame]2319<p>This unlinks the instruction from its containing basic block and deletes
2320it. If you'd just like to unlink the instruction from its containing basic
2321block but not delete it, you can use the <tt>removeFromParent()</tt> method.</p>
2322
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2323</div>
2324
2325<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2326<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2327 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
2328 <tt>Value</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2329</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2330
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2331<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2332
2333<p><i>Replacing individual instructions</i></p>
2334
2335<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]2336permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2337and <tt>ReplaceInstWithInst</tt>.</p>
2338
NAKAMURA Takumi06c6d9a2011-04-18 01:17:51 +0000[diff] [blame]2339<h5><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h5>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2340
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2341<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2342 <li><tt>ReplaceInstWithValue</tt>
2343
Nick Lewyckyb6d1f392008-09-15 06:31:52 +0000[diff] [blame]2344 <p>This function replaces all uses of a given instruction with a value,
2345 and then removes the original instruction. The following example
2346 illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2347 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2348 pointer to an integer.</p>
2349
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2350<div class="doc_code">
2351<pre>
2352AllocaInst* instToReplace = ...;
2353BasicBlock::iterator ii(instToReplace);
2354
2355ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
Daniel Dunbar58c2ac02008-10-03 22:17:25 +0000[diff] [blame]2356 Constant::getNullValue(PointerType::getUnqual(Type::Int32Ty)));
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2357</pre></div></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2358
2359 <li><tt>ReplaceInstWithInst</tt>
2360
2361 <p>This function replaces a particular instruction with another
Nick Lewyckyb6d1f392008-09-15 06:31:52 +0000[diff] [blame]2362 instruction, inserting the new instruction into the basic block at the
2363 location where the old instruction was, and replacing any uses of the old
2364 instruction with the new instruction. The following example illustrates
2365 the replacement of one <tt>AllocaInst</tt> with another.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2366
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2367<div class="doc_code">
2368<pre>
2369AllocaInst* instToReplace = ...;
2370BasicBlock::iterator ii(instToReplace);
2371
2372ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
Nick Lewycky10d64b92007-12-03 01:52:52 +0000[diff] [blame]2373 new AllocaInst(Type::Int32Ty, 0, "ptrToReplacedInt"));
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2374</pre></div></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2375</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2376
2377<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
2378
2379<p>You can use <tt>Value::replaceAllUsesWith</tt> and
2380<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]2381doxygen documentation for the <a href="/doxygen/classllvm_1_1Value.html">Value Class</a>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2382and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2383information.</p>
2384
2385<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
2386include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
2387ReplaceInstWithValue, ReplaceInstWithInst -->
2388
2389</div>
2390
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2391<!--_______________________________________________________________________-->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2392<h4>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2393 <a name="schanges_deletingGV">Deleting <tt>GlobalVariable</tt>s</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2394</h4>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2395
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2396<div>
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2397
Tanya Lattnerc5dfcdb2007-06-20 20:46:37 +0000[diff] [blame]2398<p>Deleting a global variable from a module is just as easy as deleting an
2399Instruction. First, you must have a pointer to the global variable that you wish
2400 to delete. You use this pointer to erase it from its parent, the module.
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2401 For example:</p>
2402
2403<div class="doc_code">
2404<pre>
2405<a href="#GlobalVariable">GlobalVariable</a> *GV = .. ;
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2406
Tanya Lattnerc5dfcdb2007-06-20 20:46:37 +0000[diff] [blame]2407GV-&gt;eraseFromParent();
Tanya Lattnerb011c662007-06-20 18:33:15 +0000[diff] [blame]2408</pre>
2409</div>
2410
2411</div>
2412
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2413</div>
2414
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2415<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2416<h3>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2417 <a name="create_types">How to Create Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2418</h3>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2419
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2420<div>
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2421
2422<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]2423statically, you can use <tt>TypeBuilder&lt;...&gt;::get()</tt>, defined
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2424in <tt>llvm/Support/TypeBuilder.h</tt>, to retrieve them. <tt>TypeBuilder</tt>
2425has two forms depending on whether you're building types for cross-compilation
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2426or native library use. <tt>TypeBuilder&lt;T, true&gt;</tt> requires
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2427that <tt>T</tt> be independent of the host environment, meaning that it's built
2428out of types from
2429the <a href="/doxygen/namespacellvm_1_1types.html"><tt>llvm::types</tt></a>
2430namespace and pointers, functions, arrays, etc. built of
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2431those. <tt>TypeBuilder&lt;T, false&gt;</tt> additionally allows native C types
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2432whose size may depend on the host compiler. For example,</p>
2433
2434<div class="doc_code">
2435<pre>
Misha Brukman1af789f2009-05-01 20:40:51 +0000[diff] [blame]2436FunctionType *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]2437</pre>
2438</div>
2439
2440<p>is easier to read and write than the equivalent</p>
2441
2442<div class="doc_code">
2443<pre>
Owen Anderson5e8c50e2009-06-16 17:40:28 +0000[diff] [blame]2444std::vector&lt;const Type*&gt; params;
Jeffrey Yasskin714257f2009-04-30 22:33:41 +0000[diff] [blame]2445params.push_back(PointerType::getUnqual(Type::Int32Ty));
2446FunctionType *ft = FunctionType::get(Type::Int8Ty, params, false);
2447</pre>
2448</div>
2449
2450<p>See the <a href="/doxygen/TypeBuilder_8h-source.html#l00001">class
2451comment</a> for more details.</p>
2452
2453</div>
2454
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2455</div>
2456
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2457<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2458<h2>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2459 <a name="threading">Threads and LLVM</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2460</h2>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2461<!-- *********************************************************************** -->
2462
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2463<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2464<p>
2465This section describes the interaction of the LLVM APIs with multithreading,
2466both on the part of client applications, and in the JIT, in the hosted
2467application.
2468</p>
2469
2470<p>
2471Note that LLVM's support for multithreading is still relatively young. Up
2472through version 2.5, the execution of threaded hosted applications was
2473supported, but not threaded client access to the APIs. While this use case is
2474now supported, clients <em>must</em> adhere to the guidelines specified below to
2475ensure proper operation in multithreaded mode.
2476</p>
2477
2478<p>
2479Note that, on Unix-like platforms, LLVM requires the presence of GCC's atomic
2480intrinsics in order to support threaded operation. If you need a
2481multhreading-capable LLVM on a platform without a suitably modern system
2482compiler, consider compiling LLVM and LLVM-GCC in single-threaded mode, and
2483using the resultant compiler to build a copy of LLVM with multithreading
2484support.
2485</p>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2486
2487<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2488<h3>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2489 <a name="startmultithreaded">Entering and Exiting Multithreaded Mode</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2490</h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2491
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2492<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2493
2494<p>
2495In order to properly protect its internal data structures while avoiding
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2496excessive locking overhead in the single-threaded case, the LLVM must intialize
2497certain data structures necessary to provide guards around its internals. To do
2498so, the client program must invoke <tt>llvm_start_multithreaded()</tt> before
2499making any concurrent LLVM API calls. To subsequently tear down these
2500structures, use the <tt>llvm_stop_multithreaded()</tt> call. You can also use
2501the <tt>llvm_is_multithreaded()</tt> call to check the status of multithreaded
2502mode.
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2503</p>
2504
2505<p>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2506Note that both of these calls must be made <em>in isolation</em>. That is to
2507say that no other LLVM API calls may be executing at any time during the
2508execution of <tt>llvm_start_multithreaded()</tt> or <tt>llvm_stop_multithreaded
2509</tt>. It's is the client's responsibility to enforce this isolation.
2510</p>
2511
2512<p>
2513The return value of <tt>llvm_start_multithreaded()</tt> indicates the success or
2514failure of the initialization. Failure typically indicates that your copy of
2515LLVM was built without multithreading support, typically because GCC atomic
2516intrinsics were not found in your system compiler. In this case, the LLVM API
2517will not be safe for concurrent calls. However, it <em>will</em> be safe for
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2518hosting threaded applications in the JIT, though <a href="#jitthreading">care
2519must be taken</a> to ensure that side exits and the like do not accidentally
2520result in concurrent LLVM API calls.
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2521</p>
2522</div>
2523
2524<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2525<h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2526 <a name="shutdown">Ending Execution with <tt>llvm_shutdown()</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2527</h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2528
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2529<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2530<p>
2531When you are done using the LLVM APIs, you should call <tt>llvm_shutdown()</tt>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2532to deallocate memory used for internal structures. This will also invoke
2533<tt>llvm_stop_multithreaded()</tt> if LLVM is operating in multithreaded mode.
2534As such, <tt>llvm_shutdown()</tt> requires the same isolation guarantees as
2535<tt>llvm_stop_multithreaded()</tt>.
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2536</p>
2537
2538<p>
2539Note that, if you use scope-based shutdown, you can use the
2540<tt>llvm_shutdown_obj</tt> class, which calls <tt>llvm_shutdown()</tt> in its
2541destructor.
2542</div>
2543
2544<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2545<h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2546 <a name="managedstatic">Lazy Initialization with <tt>ManagedStatic</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2547</h3>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2548
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2549<div>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2550<p>
2551<tt>ManagedStatic</tt> is a utility class in LLVM used to implement static
2552initialization of static resources, such as the global type tables. Before the
2553invocation of <tt>llvm_shutdown()</tt>, it implements a simple lazy
2554initialization scheme. Once <tt>llvm_start_multithreaded()</tt> returns,
2555however, it uses double-checked locking to implement thread-safe lazy
2556initialization.
2557</p>
2558
2559<p>
2560Note that, because no other threads are allowed to issue LLVM API calls before
2561<tt>llvm_start_multithreaded()</tt> returns, it is possible to have
2562<tt>ManagedStatic</tt>s of <tt>llvm::sys::Mutex</tt>s.
2563</p>
Owen Anderson1ad70e32009-06-16 18:04:19 +0000[diff] [blame]2564
2565<p>
2566The <tt>llvm_acquire_global_lock()</tt> and <tt>llvm_release_global_lock</tt>
2567APIs provide access to the global lock used to implement the double-checked
2568locking for lazy initialization. These should only be used internally to LLVM,
2569and only if you know what you're doing!
2570</p>
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2571</div>
2572
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2573<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2574<h3>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2575 <a name="llvmcontext">Achieving Isolation with <tt>LLVMContext</tt></a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2576</h3>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2577
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2578<div>
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2579<p>
2580<tt>LLVMContext</tt> is an opaque class in the LLVM API which clients can use
2581to operate multiple, isolated instances of LLVM concurrently within the same
2582address space. For instance, in a hypothetical compile-server, the compilation
2583of an individual translation unit is conceptually independent from all the
2584others, and it would be desirable to be able to compile incoming translation
2585units concurrently on independent server threads. Fortunately,
2586<tt>LLVMContext</tt> exists to enable just this kind of scenario!
2587</p>
2588
2589<p>
2590Conceptually, <tt>LLVMContext</tt> provides isolation. Every LLVM entity
2591(<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]2592in LLVM's in-memory IR belongs to an <tt>LLVMContext</tt>. Entities in
Owen Andersone0c951a2009-08-19 17:58:52 +0000[diff] [blame]2593different contexts <em>cannot</em> interact with each other: <tt>Module</tt>s in
2594different contexts cannot be linked together, <tt>Function</tt>s cannot be added
2595to <tt>Module</tt>s in different contexts, etc. What this means is that is is
2596safe to compile on multiple threads simultaneously, as long as no two threads
2597operate on entities within the same context.
2598</p>
2599
2600<p>
2601In practice, very few places in the API require the explicit specification of a
2602<tt>LLVMContext</tt>, other than the <tt>Type</tt> creation/lookup APIs.
2603Because every <tt>Type</tt> carries a reference to its owning context, most
2604other entities can determine what context they belong to by looking at their
2605own <tt>Type</tt>. If you are adding new entities to LLVM IR, please try to
2606maintain this interface design.
2607</p>
2608
2609<p>
2610For clients that do <em>not</em> require the benefits of isolation, LLVM
2611provides a convenience API <tt>getGlobalContext()</tt>. This returns a global,
2612lazily initialized <tt>LLVMContext</tt> that may be used in situations where
2613isolation is not a concern.
2614</p>
2615</div>
2616
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2617<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2618<h3>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2619 <a name="jitthreading">Threads and the JIT</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2620</h3>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2621
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2622<div>
Jeffrey Yasskin01eba392010-01-29 19:10:38 +0000[diff] [blame]2623<p>
2624LLVM's "eager" JIT compiler is safe to use in threaded programs. Multiple
2625threads can call <tt>ExecutionEngine::getPointerToFunction()</tt> or
2626<tt>ExecutionEngine::runFunction()</tt> concurrently, and multiple threads can
2627run code output by the JIT concurrently. The user must still ensure that only
2628one thread accesses IR in a given <tt>LLVMContext</tt> while another thread
2629might be modifying it. One way to do that is to always hold the JIT lock while
2630accessing IR outside the JIT (the JIT <em>modifies</em> the IR by adding
2631<tt>CallbackVH</tt>s). Another way is to only
2632call <tt>getPointerToFunction()</tt> from the <tt>LLVMContext</tt>'s thread.
2633</p>
2634
2635<p>When the JIT is configured to compile lazily (using
2636<tt>ExecutionEngine::DisableLazyCompilation(false)</tt>), there is currently a
2637<a href="http://llvm.org/bugs/show_bug.cgi?id=5184">race condition</a> in
2638updating call sites after a function is lazily-jitted. It's still possible to
2639use the lazy JIT in a threaded program if you ensure that only one thread at a
2640time can call any particular lazy stub and that the JIT lock guards any IR
2641access, but we suggest using only the eager JIT in threaded programs.
2642</p>
2643</div>
2644
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2645</div>
2646
Owen Anderson8bc1b3b2009-06-16 01:17:16 +0000[diff] [blame]2647<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2648<h2>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2649 <a name="advanced">Advanced Topics</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2650</h2>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2651<!-- *********************************************************************** -->
2652
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2653<div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]2654<p>
2655This section describes some of the advanced or obscure API's that most clients
2656do not need to be aware of. These API's tend manage the inner workings of the
2657LLVM system, and only need to be accessed in unusual circumstances.
2658</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2659
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2660
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]2661<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2662<h3>
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2663 <a name="SymbolTable">The <tt>ValueSymbolTable</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2664</h3>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]2665
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2666<div>
Chris Lattner263a98e2007-02-16 04:37:31 +0000[diff] [blame]2667<p>The <tt><a href="http://llvm.org/doxygen/classllvm_1_1ValueSymbolTable.html">
2668ValueSymbolTable</a></tt> class provides a symbol table that the <a
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2669href="#Function"><tt>Function</tt></a> and <a href="#Module">
Chris Lattner263a98e2007-02-16 04:37:31 +0000[diff] [blame]2670<tt>Module</tt></a> classes use for naming value definitions. The symbol table
2671can provide a name for any <a href="#Value"><tt>Value</tt></a>.
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2672</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2673
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]2674<p>Note that the <tt>SymbolTable</tt> class should not be directly accessed
2675by most clients. It should only be used when iteration over the symbol table
2676names themselves are required, which is very special purpose. Note that not
2677all LLVM
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2678<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]2679an empty name) do not exist in the symbol table.
2680</p>
2681
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2682<p>Symbol tables support iteration over the values in the symbol
Chris Lattner263a98e2007-02-16 04:37:31 +0000[diff] [blame]2683table with <tt>begin/end/iterator</tt> and supports querying to see if a
2684specific name is in the symbol table (with <tt>lookup</tt>). The
2685<tt>ValueSymbolTable</tt> class exposes no public mutator methods, instead,
2686simply call <tt>setName</tt> on a value, which will autoinsert it into the
Chris Lattner1afcace2011-07-09 17:41:24 +0000[diff] [blame]2687appropriate symbol table.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2688
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2689</div>
2690
2691
2692
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2693<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2694<h3>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2695 <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]2696</h3>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2697
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2698<div>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2699<p>The <tt><a href="http://llvm.org/doxygen/classllvm_1_1User.html">
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2700User</a></tt> class provides a basis for expressing the ownership of <tt>User</tt>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2701towards other <tt><a href="http://llvm.org/doxygen/classllvm_1_1Value.html">
2702Value</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]2703Use</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]2704addition and removal.</p>
2705
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2706<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2707<h4>
2708 <a name="Use2User">
2709 Interaction and relationship between <tt>User</tt> and <tt>Use</tt> objects
2710 </a>
2711</h4>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2712
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2713<div>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2714<p>
2715A subclass of <tt>User</tt> can choose between incorporating its <tt>Use</tt> objects
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2716or refer to them out-of-line by means of a pointer. A mixed variant
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2717(some <tt>Use</tt>s inline others hung off) is impractical and breaks the invariant
2718that the <tt>Use</tt> objects belonging to the same <tt>User</tt> form a contiguous array.
2719</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2720
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2721<p>
2722We have 2 different layouts in the <tt>User</tt> (sub)classes:
2723<ul>
2724<li><p>Layout a)
2725The <tt>Use</tt> object(s) are inside (resp. at fixed offset) of the <tt>User</tt>
2726object and there are a fixed number of them.</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2727
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2728<li><p>Layout b)
2729The <tt>Use</tt> object(s) are referenced by a pointer to an
2730array from the <tt>User</tt> object and there may be a variable
2731number of them.</p>
2732</ul>
2733<p>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2734As of v2.4 each layout still possesses a direct pointer to the
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2735start of the array of <tt>Use</tt>s. Though not mandatory for layout a),
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2736we stick to this redundancy for the sake of simplicity.
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2737The <tt>User</tt> object also stores the number of <tt>Use</tt> objects it
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2738has. (Theoretically this information can also be calculated
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2739given the scheme presented below.)</p>
2740<p>
2741Special forms of allocation operators (<tt>operator new</tt>)
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2742enforce the following memory layouts:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2743
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2744<ul>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2745<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]2746
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2747<pre>
2748...---.---.---.---.-------...
2749 | P | P | P | P | User
2750'''---'---'---'---'-------'''
2751</pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2752
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2753<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]2754<pre>
2755.-------...
2756| User
2757'-------'''
2758 |
2759 v
2760 .---.---.---.---...
2761 | P | P | P | P |
2762 '---'---'---'---'''
2763</pre>
2764</ul>
2765<i>(In the above figures '<tt>P</tt>' stands for the <tt>Use**</tt> that
2766 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]2767
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2768</div>
2769
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2770<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2771<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2772 <a name="Waymarking">The waymarking algorithm</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2773</h4>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2774
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2775<div>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2776<p>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2777Since the <tt>Use</tt> objects are deprived of the direct (back)pointer to
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2778their <tt>User</tt> objects, there must be a fast and exact method to
2779recover it. This is accomplished by the following scheme:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2780
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2781A 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]2782start of the <tt>User</tt> object:
2783<ul>
2784<li><tt>00</tt> &mdash;&gt; binary digit 0</li>
2785<li><tt>01</tt> &mdash;&gt; binary digit 1</li>
2786<li><tt>10</tt> &mdash;&gt; stop and calculate (<tt>s</tt>)</li>
2787<li><tt>11</tt> &mdash;&gt; full stop (<tt>S</tt>)</li>
2788</ul>
2789<p>
2790Given a <tt>Use*</tt>, all we have to do is to walk till we get
2791a stop and we either have a <tt>User</tt> immediately behind or
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2792we have to walk to the next stop picking up digits
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2793and calculating the offset:</p>
2794<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2795.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.---.----------------
2796| 1 | s | 1 | 0 | 1 | 0 | s | 1 | 1 | 0 | s | 1 | 1 | s | 1 | S | User (or User*)
2797'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'---'----------------
2798 |+15 |+10 |+6 |+3 |+1
2799 | | | | |__>
2800 | | | |__________>
2801 | | |______________________>
2802 | |______________________________________>
2803 |__________________________________________________________>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2804</pre>
2805<p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2806Only the significant number of bits need to be stored between the
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2807stops, so that the <i>worst case is 20 memory accesses</i> when there are
28081000 <tt>Use</tt> objects associated with a <tt>User</tt>.</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2809
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2810</div>
2811
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2812<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2813<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2814 <a name="ReferenceImpl">Reference implementation</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2815</h4>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2816
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2817<div>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2818<p>
2819The following literate Haskell fragment demonstrates the concept:</p>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2820
2821<div class="doc_code">
2822<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2823> import Test.QuickCheck
2824>
2825> digits :: Int -> [Char] -> [Char]
2826> digits 0 acc = '0' : acc
2827> digits 1 acc = '1' : acc
2828> digits n acc = digits (n `div` 2) $ digits (n `mod` 2) acc
2829>
2830> dist :: Int -> [Char] -> [Char]
2831> dist 0 [] = ['S']
2832> dist 0 acc = acc
2833> dist 1 acc = let r = dist 0 acc in 's' : digits (length r) r
2834> dist n acc = dist (n - 1) $ dist 1 acc
2835>
2836> takeLast n ss = reverse $ take n $ reverse ss
2837>
2838> test = takeLast 40 $ dist 20 []
2839>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2840</pre>
2841</div>
2842<p>
2843Printing &lt;test&gt; gives: <tt>"1s100000s11010s10100s1111s1010s110s11s1S"</tt></p>
2844<p>
2845The reverse algorithm computes the length of the string just by examining
2846a certain prefix:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2847
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2848<div class="doc_code">
2849<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2850> pref :: [Char] -> Int
2851> pref "S" = 1
2852> pref ('s':'1':rest) = decode 2 1 rest
2853> pref (_:rest) = 1 + pref rest
2854>
2855> decode walk acc ('0':rest) = decode (walk + 1) (acc * 2) rest
2856> decode walk acc ('1':rest) = decode (walk + 1) (acc * 2 + 1) rest
2857> decode walk acc _ = walk + acc
2858>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2859</pre>
2860</div>
2861<p>
2862Now, as expected, printing &lt;pref test&gt; gives <tt>40</tt>.</p>
2863<p>
2864We can <i>quickCheck</i> this with following property:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2865
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2866<div class="doc_code">
2867<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2868> testcase = dist 2000 []
2869> testcaseLength = length testcase
2870>
2871> identityProp n = n > 0 && n <= testcaseLength ==> length arr == pref arr
2872> where arr = takeLast n testcase
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2873>
2874</pre>
2875</div>
2876<p>
2877As expected &lt;quickCheck identityProp&gt; gives:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2878
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2879<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2880*Main> quickCheck identityProp
2881OK, passed 100 tests.
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2882</pre>
2883<p>
2884Let's be a bit more exhaustive:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2885
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2886<div class="doc_code">
2887<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2888>
2889> deepCheck p = check (defaultConfig { configMaxTest = 500 }) p
2890>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2891</pre>
2892</div>
2893<p>
2894And here is the result of &lt;deepCheck identityProp&gt;:</p>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2895
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2896<pre>
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2897*Main> deepCheck identityProp
2898OK, passed 500 tests.
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2899</pre>
2900
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2901</div>
2902
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2903<!-- ______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2904<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2905 <a name="Tagging">Tagging considerations</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2906</h4>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2907
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2908<div>
2909
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2910<p>
2911To maintain the invariant that the 2 LSBits of each <tt>Use**</tt> in <tt>Use</tt>
2912never change after being set up, setters of <tt>Use::Prev</tt> must re-tag the
2913new <tt>Use**</tt> on every modification. Accordingly getters must strip the
2914tag bits.</p>
2915<p>
Gabor Greifd41720a2008-06-25 00:10:22 +0000[diff] [blame]2916For layout b) instead of the <tt>User</tt> we find a pointer (<tt>User*</tt> with LSBit set).
2917Following this pointer brings us to the <tt>User</tt>. A portable trick ensures
2918that the first bytes of <tt>User</tt> (if interpreted as a pointer) never has
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2919the LSBit set. (Portability is relying on the fact that all known compilers place the
2920<tt>vptr</tt> in the first word of the instances.)</p>
Gabor Greifdfed1182008-06-18 13:44:57 +0000[diff] [blame]2921
Gabor Greife98fc272008-06-16 21:06:12 +0000[diff] [blame]2922</div>
2923
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2924</div>
2925
2926</div>
2927
2928<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2929<h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2930 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2931</h2>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2932<!-- *********************************************************************** -->
2933
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2934<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2935<p><tt>#include "<a href="/doxygen/Type_8h-source.html">llvm/Type.h</a>"</tt>
2936<br>doxygen info: <a href="/doxygen/classllvm_1_1Type.html">Type Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2937
2938<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2939being inspected or transformed. The core LLVM classes are defined in
2940header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2941the <tt>lib/VMCore</tt> directory.</p>
2942
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2943<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2944<h3>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2945 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2946</h3>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2947
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2948<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2949
2950 <p><tt>Type</tt> is a superclass of all type classes. Every <tt>Value</tt> has
2951 a <tt>Type</tt>. <tt>Type</tt> cannot be instantiated directly but only
2952 through its subclasses. Certain primitive types (<tt>VoidType</tt>,
2953 <tt>LabelType</tt>, <tt>FloatType</tt> and <tt>DoubleType</tt>) have hidden
2954 subclasses. They are hidden because they offer no useful functionality beyond
2955 what the <tt>Type</tt> class offers except to distinguish themselves from
2956 other subclasses of <tt>Type</tt>.</p>
2957 <p>All other types are subclasses of <tt>DerivedType</tt>. Types can be
2958 named, but this is not a requirement. There exists exactly
2959 one instance of a given shape at any one time. This allows type equality to
2960 be performed with address equality of the Type Instance. That is, given two
2961 <tt>Type*</tt> values, the types are identical if the pointers are identical.
2962 </p>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2963
2964<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2965<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2966 <a name="m_Type">Important Public Methods</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2967</h4>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2968
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2969<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2970
2971<ul>
Duncan Sandsb0bc6c32010-02-15 16:12:20 +0000[diff] [blame]2972 <li><tt>bool isIntegerTy() const</tt>: Returns true for any integer type.</li>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2973
Duncan Sandsb0bc6c32010-02-15 16:12:20 +0000[diff] [blame]2974 <li><tt>bool isFloatingPointTy()</tt>: Return true if this is one of the five
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2975 floating point types.</li>
2976
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2977 <li><tt>bool isSized()</tt>: Return true if the type has known size. Things
2978 that don't have a size are abstract types, labels and void.</li>
2979
2980</ul>
2981</div>
2982
2983<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2984<h4>
Gabor Greiffd095b62009-01-05 16:05:32 +0000[diff] [blame]2985 <a name="derivedtypes">Important Derived Types</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]2986</h4>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]2987<div>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2988<dl>
2989 <dt><tt>IntegerType</tt></dt>
2990 <dd>Subclass of DerivedType that represents integer types of any bit width.
2991 Any bit width between <tt>IntegerType::MIN_INT_BITS</tt> (1) and
2992 <tt>IntegerType::MAX_INT_BITS</tt> (~8 million) can be represented.
2993 <ul>
2994 <li><tt>static const IntegerType* get(unsigned NumBits)</tt>: get an integer
2995 type of a specific bit width.</li>
2996 <li><tt>unsigned getBitWidth() const</tt>: Get the bit width of an integer
2997 type.</li>
2998 </ul>
2999 </dd>
3000 <dt><tt>SequentialType</tt></dt>
Tobias Grosserd475c102011-07-12 11:37:02 +0000[diff] [blame]3001 <dd>This is subclassed by ArrayType, PointerType and VectorType.
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3002 <ul>
3003 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
3004 of the elements in the sequential type. </li>
3005 </ul>
3006 </dd>
3007 <dt><tt>ArrayType</tt></dt>
3008 <dd>This is a subclass of SequentialType and defines the interface for array
3009 types.
3010 <ul>
3011 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
3012 elements in the array. </li>
3013 </ul>
3014 </dd>
3015 <dt><tt>PointerType</tt></dt>
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]3016 <dd>Subclass of SequentialType for pointer types.</dd>
Reid Spencer9d6565a2007-02-15 02:26:10 +0000[diff] [blame]3017 <dt><tt>VectorType</tt></dt>
Reid Spencer485bad12007-02-15 03:07:05 +0000[diff] [blame]3018 <dd>Subclass of SequentialType for vector types. A
3019 vector type is similar to an ArrayType but is distinguished because it is
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3020 a first class type whereas ArrayType is not. Vector types are used for
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3021 vector operations and are usually small vectors of of an integer or floating
3022 point type.</dd>
3023 <dt><tt>StructType</tt></dt>
3024 <dd>Subclass of DerivedTypes for struct types.</dd>
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]3025 <dt><tt><a name="FunctionType">FunctionType</a></tt></dt>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3026 <dd>Subclass of DerivedTypes for function types.
3027 <ul>
Dan Gohman4bb31bf2010-03-30 20:04:57 +0000[diff] [blame]3028 <li><tt>bool isVarArg() const</tt>: Returns true if it's a vararg
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3029 function</li>
3030 <li><tt> const Type * getReturnType() const</tt>: Returns the
3031 return type of the function.</li>
3032 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
3033 the type of the ith parameter.</li>
3034 <li><tt> const unsigned getNumParams() const</tt>: Returns the
3035 number of formal parameters.</li>
3036 </ul>
3037 </dd>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3038</dl>
3039</div>
3040
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3041</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3042
3043<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3044<h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3045 <a name="Module">The <tt>Module</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3046</h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3047
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3048<div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3049
3050<p><tt>#include "<a
3051href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
3052<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
3053
3054<p>The <tt>Module</tt> class represents the top level structure present in LLVM
3055programs. An LLVM module is effectively either a translation unit of the
3056original program or a combination of several translation units merged by the
3057linker. The <tt>Module</tt> class keeps track of a list of <a
3058href="#Function"><tt>Function</tt></a>s, a list of <a
3059href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
3060href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
3061helpful member functions that try to make common operations easy.</p>
3062
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3063<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3064<h4>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3065 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3066</h4>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3067
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3068<div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3069
3070<ul>
3071 <li><tt>Module::Module(std::string name = "")</tt></li>
3072</ul>
3073
3074<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
3075provide a name for it (probably based on the name of the translation unit).</p>
3076
3077<ul>
3078 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
3079 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
3080
3081 <tt>begin()</tt>, <tt>end()</tt>
3082 <tt>size()</tt>, <tt>empty()</tt>
3083
3084 <p>These are forwarding methods that make it easy to access the contents of
3085 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
3086 list.</p></li>
3087
3088 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
3089
3090 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
3091 necessary to use when you need to update the list or perform a complex
3092 action that doesn't have a forwarding method.</p>
3093
3094 <p><!-- Global Variable --></p></li>
3095</ul>
3096
3097<hr>
3098
3099<ul>
3100 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
3101
3102 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
3103
3104 <tt>global_begin()</tt>, <tt>global_end()</tt>
3105 <tt>global_size()</tt>, <tt>global_empty()</tt>
3106
3107 <p> These are forwarding methods that make it easy to access the contents of
3108 a <tt>Module</tt> object's <a
3109 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
3110
3111 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
3112
3113 <p>Returns the list of <a
3114 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
3115 use when you need to update the list or perform a complex action that
3116 doesn't have a forwarding method.</p>
3117
3118 <p><!-- Symbol table stuff --> </p></li>
3119</ul>
3120
3121<hr>
3122
3123<ul>
3124 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
3125
3126 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
3127 for this <tt>Module</tt>.</p>
3128
3129 <p><!-- Convenience methods --></p></li>
3130</ul>
3131
3132<hr>
3133
3134<ul>
3135 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
3136 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
3137
3138 <p>Look up the specified function in the <tt>Module</tt> <a
3139 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
3140 <tt>null</tt>.</p></li>
3141
3142 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
3143 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
3144
3145 <p>Look up the specified function in the <tt>Module</tt> <a
3146 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
3147 external declaration for the function and return it.</p></li>
3148
3149 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
3150
3151 <p>If there is at least one entry in the <a
3152 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
3153 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
3154 string.</p></li>
3155
3156 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
3157 href="#Type">Type</a> *Ty)</tt>
3158
3159 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
3160 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
3161 name, true is returned and the <a
3162 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
3163</ul>
3164
3165</div>
3166
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3167</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3168
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]3169<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3170<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3171 <a name="Value">The <tt>Value</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3172</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3173
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3174<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3175
3176<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
3177<br>
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]3178doxygen info: <a href="/doxygen/classllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3179
3180<p>The <tt>Value</tt> class is the most important class in the LLVM Source
3181base. It represents a typed value that may be used (among other things) as an
3182operand to an instruction. There are many different types of <tt>Value</tt>s,
3183such as <a href="#Constant"><tt>Constant</tt></a>s,<a
3184href="#Argument"><tt>Argument</tt></a>s. Even <a
3185href="#Instruction"><tt>Instruction</tt></a>s and <a
3186href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
3187
3188<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
3189for a program. For example, an incoming argument to a function (represented
3190with an instance of the <a href="#Argument">Argument</a> class) is "used" by
3191every instruction in the function that references the argument. To keep track
3192of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
3193href="#User"><tt>User</tt></a>s that is using it (the <a
3194href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
3195graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
3196def-use information in the program, and is accessible through the <tt>use_</tt>*
3197methods, shown below.</p>
3198
3199<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
3200and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
3201method. In addition, all LLVM values can be named. The "name" of the
3202<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
3203
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]3204<div class="doc_code">
3205<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]3206%<b>foo</b> = add i32 1, 2
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]3207</pre>
3208</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3209
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]3210<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]3211that the name of any value may be missing (an empty string), so names should
3212<b>ONLY</b> be used for debugging (making the source code easier to read,
3213debugging printouts), they should not be used to keep track of values or map
3214between them. For this purpose, use a <tt>std::map</tt> of pointers to the
3215<tt>Value</tt> itself instead.</p>
3216
3217<p>One important aspect of LLVM is that there is no distinction between an SSA
3218variable and the operation that produces it. Because of this, any reference to
3219the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]3220argument, for example) is represented as a direct pointer to the instance of
3221the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3222represents this value. Although this may take some getting used to, it
3223simplifies the representation and makes it easier to manipulate.</p>
3224
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3225<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3226<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3227 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3228</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3229
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3230<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3231
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3232<ul>
3233 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
3234use-list<br>
Gabor Greifbbbf9a22010-03-26 19:59:25 +0000[diff] [blame]3235 <tt>Value::const_use_iterator</tt> - Typedef for const_iterator over
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3236the use-list<br>
3237 <tt>unsigned use_size()</tt> - Returns the number of users of the
3238value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3239 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3240 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
3241the use-list.<br>
3242 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
3243use-list.<br>
3244 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
3245element in the list.
3246 <p> These methods are the interface to access the def-use
3247information in LLVM. As with all other iterators in LLVM, the naming
3248conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3249 </li>
3250 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3251 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3252 </li>
3253 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3254 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3255 <tt>void setName(const std::string &amp;Name)</tt>
3256 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
3257be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3258 </li>
3259 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3260
3261 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
3262 href="#User"><tt>User</tt>s</a> of the current value to refer to
3263 "<tt>V</tt>" instead. For example, if you detect that an instruction always
3264 produces a constant value (for example through constant folding), you can
3265 replace all uses of the instruction with the constant like this:</p>
3266
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]3267<div class="doc_code">
3268<pre>
3269Inst-&gt;replaceAllUsesWith(ConstVal);
3270</pre>
3271</div>
3272
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3273</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3274
3275</div>
3276
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3277</div>
3278
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3279<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3280<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3281 <a name="User">The <tt>User</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3282</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3283
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3284<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3285
3286<p>
3287<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]3288doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3289Superclass: <a href="#Value"><tt>Value</tt></a></p>
3290
3291<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
3292refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
3293that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
3294referring to. The <tt>User</tt> class itself is a subclass of
3295<tt>Value</tt>.</p>
3296
3297<p>The operands of a <tt>User</tt> point directly to the LLVM <a
3298href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
3299Single Assignment (SSA) form, there can only be one definition referred to,
3300allowing this direct connection. This connection provides the use-def
3301information in LLVM.</p>
3302
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3303<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3304<h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3305 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3306</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3307
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3308<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3309
3310<p>The <tt>User</tt> class exposes the operand list in two ways: through
3311an index access interface and through an iterator based interface.</p>
3312
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3313<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3314 <li><tt>Value *getOperand(unsigned i)</tt><br>
3315 <tt>unsigned getNumOperands()</tt>
3316 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3317convenient form for direct access.</p></li>
3318
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3319 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
3320list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]3321 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
3322the operand list.<br>
3323 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3324operand list.
3325 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3326the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3327</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3328
3329</div>
3330
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3331</div>
3332
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3333<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3334<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3335 <a name="Instruction">The <tt>Instruction</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3336</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3337
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3338<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3339
3340<p><tt>#include "</tt><tt><a
3341href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]3342doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3343Superclasses: <a href="#User"><tt>User</tt></a>, <a
3344href="#Value"><tt>Value</tt></a></p>
3345
3346<p>The <tt>Instruction</tt> class is the common base class for all LLVM
3347instructions. It provides only a few methods, but is a very commonly used
3348class. The primary data tracked by the <tt>Instruction</tt> class itself is the
3349opcode (instruction type) and the parent <a
3350href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
3351into. To represent a specific type of instruction, one of many subclasses of
3352<tt>Instruction</tt> are used.</p>
3353
3354<p> Because the <tt>Instruction</tt> class subclasses the <a
3355href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
3356way as for other <a href="#User"><tt>User</tt></a>s (with the
3357<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
3358<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
3359the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
3360file contains some meta-data about the various different types of instructions
3361in LLVM. It describes the enum values that are used as opcodes (for example
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]3362<tt>Instruction::Add</tt> and <tt>Instruction::ICmp</tt>), as well as the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3363concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
3364example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]3365href="#CmpInst">CmpInst</a></tt>). Unfortunately, the use of macros in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3366this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]3367<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3368
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3369<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3370<h4>
3371 <a name="s_Instruction">
3372 Important Subclasses of the <tt>Instruction</tt> class
3373 </a>
3374</h4>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3375<div>
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]3376 <ul>
3377 <li><tt><a name="BinaryOperator">BinaryOperator</a></tt>
3378 <p>This subclasses represents all two operand instructions whose operands
3379 must be the same type, except for the comparison instructions.</p></li>
3380 <li><tt><a name="CastInst">CastInst</a></tt>
3381 <p>This subclass is the parent of the 12 casting instructions. It provides
3382 common operations on cast instructions.</p>
3383 <li><tt><a name="CmpInst">CmpInst</a></tt>
3384 <p>This subclass respresents the two comparison instructions,
3385 <a href="LangRef.html#i_icmp">ICmpInst</a> (integer opreands), and
3386 <a href="LangRef.html#i_fcmp">FCmpInst</a> (floating point operands).</p>
3387 <li><tt><a name="TerminatorInst">TerminatorInst</a></tt>
3388 <p>This subclass is the parent of all terminator instructions (those which
3389 can terminate a block).</p>
3390 </ul>
3391 </div>
3392
3393<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3394<h4>
3395 <a name="m_Instruction">
3396 Important Public Members of the <tt>Instruction</tt> class
3397 </a>
3398</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3399
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3400<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3401
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3402<ul>
3403 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3404 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
3405this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3406 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3407 <p>Returns true if the instruction writes to memory, i.e. it is a
3408 <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]3409 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3410 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3411 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3412 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3413in all ways to the original except that the instruction has no parent
3414(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3415and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3416</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3417
3418</div>
3419
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3420</div>
3421
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3422<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3423<h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3424 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3425</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3426
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3427<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3428
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3429<p>Constant represents a base class for different types of constants. It
3430is subclassed by ConstantInt, ConstantArray, etc. for representing
3431the various types of Constants. <a href="#GlobalValue">GlobalValue</a> is also
3432a subclass, which represents the address of a global variable or function.
3433</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3434
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3435<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3436<h4>Important Subclasses of Constant</h4>
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3437<div>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3438<ul>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3439 <li>ConstantInt : This subclass of Constant represents an integer constant of
3440 any width.
3441 <ul>
Reid Spencer97b4ee32007-03-01 21:05:33 +0000[diff] [blame]3442 <li><tt>const APInt&amp; getValue() const</tt>: Returns the underlying
3443 value of this constant, an APInt value.</li>
3444 <li><tt>int64_t getSExtValue() const</tt>: Converts the underlying APInt
3445 value to an int64_t via sign extension. If the value (not the bit width)
3446 of the APInt is too large to fit in an int64_t, an assertion will result.
3447 For this reason, use of this method is discouraged.</li>
3448 <li><tt>uint64_t getZExtValue() const</tt>: Converts the underlying APInt
3449 value to a uint64_t via zero extension. IF the value (not the bit width)
3450 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]3451 For this reason, use of this method is discouraged.</li>
Reid Spencer97b4ee32007-03-01 21:05:33 +0000[diff] [blame]3452 <li><tt>static ConstantInt* get(const APInt&amp; Val)</tt>: Returns the
3453 ConstantInt object that represents the value provided by <tt>Val</tt>.
3454 The type is implied as the IntegerType that corresponds to the bit width
3455 of <tt>Val</tt>.</li>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3456 <li><tt>static ConstantInt* get(const Type *Ty, uint64_t Val)</tt>:
3457 Returns the ConstantInt object that represents the value provided by
3458 <tt>Val</tt> for integer type <tt>Ty</tt>.</li>
3459 </ul>
3460 </li>
3461 <li>ConstantFP : This class represents a floating point constant.
3462 <ul>
3463 <li><tt>double getValue() const</tt>: Returns the underlying value of
3464 this constant. </li>
3465 </ul>
3466 </li>
3467 <li>ConstantArray : This represents a constant array.
3468 <ul>
3469 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
3470 a vector of component constants that makeup this array. </li>
3471 </ul>
3472 </li>
3473 <li>ConstantStruct : This represents a constant struct.
3474 <ul>
3475 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
3476 a vector of component constants that makeup this array. </li>
3477 </ul>
3478 </li>
3479 <li>GlobalValue : This represents either a global variable or a function. In
3480 either case, the value is a constant fixed address (after linking).
3481 </li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3482</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3483</div>
3484
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3485</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3486
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3487<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3488<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3489 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3490</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3491
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3492<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3493
3494<p><tt>#include "<a
3495href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]3496doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
3497Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3498Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
3499<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]3500
3501<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
3502href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
3503visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
3504Because they are visible at global scope, they are also subject to linking with
3505other globals defined in different translation units. To control the linking
3506process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
3507<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]3508defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3509
3510<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
3511<tt>static</tt> in C), it is not visible to code outside the current translation
3512unit, and does not participate in linking. If it has external linkage, it is
3513visible to external code, and does participate in linking. In addition to
3514linkage information, <tt>GlobalValue</tt>s keep track of which <a
3515href="#Module"><tt>Module</tt></a> they are currently part of.</p>
3516
3517<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
3518by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
3519global is always a pointer to its contents. It is important to remember this
3520when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
3521be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
3522subclass 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]3523i32]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3524the address of the first element of this array and the value of the
3525<tt>GlobalVariable</tt> are the same, they have different types. The
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]3526<tt>GlobalVariable</tt>'s type is <tt>[24 x i32]</tt>. The first element's type
3527is <tt>i32.</tt> Because of this, accessing a global value requires you to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3528dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
3529can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
3530Language Reference Manual</a>.</p>
3531
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3532<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3533<h4>
3534 <a name="m_GlobalValue">
3535 Important Public Members of the <tt>GlobalValue</tt> class
3536 </a>
3537</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3538
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3539<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3540
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3541<ul>
3542 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3543 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3544 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
3545 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
3546 <p> </p>
3547 </li>
3548 <li><tt><a href="#Module">Module</a> *getParent()</tt>
3549 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3550GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3551</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3552
3553</div>
3554
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3555</div>
3556
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3557<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3558<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3559 <a name="Function">The <tt>Function</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3560</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3561
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3562<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3563
3564<p><tt>#include "<a
3565href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]3566info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3567Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
3568<a href="#Constant"><tt>Constant</tt></a>,
3569<a href="#User"><tt>User</tt></a>,
3570<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3571
3572<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
Torok Edwin87469292009-10-12 13:37:29 +0000[diff] [blame]3573actually one of the more complex classes in the LLVM hierarchy because it must
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3574keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3575of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
3576<a href="#Argument"><tt>Argument</tt></a>s, and a
3577<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3578
3579<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
3580commonly used part of <tt>Function</tt> objects. The list imposes an implicit
3581ordering of the blocks in the function, which indicate how the code will be
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3582laid out by the backend. Additionally, the first <a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3583href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
3584<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
3585block. There are no implicit exit nodes, and in fact there may be multiple exit
3586nodes from a single <tt>Function</tt>. If the <a
3587href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
3588the <tt>Function</tt> is actually a function declaration: the actual body of the
3589function hasn't been linked in yet.</p>
3590
3591<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
3592<tt>Function</tt> class also keeps track of the list of formal <a
3593href="#Argument"><tt>Argument</tt></a>s that the function receives. This
3594container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
3595nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
3596the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
3597
3598<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
3599LLVM feature that is only used when you have to look up a value by name. Aside
3600from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
3601internally to make sure that there are not conflicts between the names of <a
3602href="#Instruction"><tt>Instruction</tt></a>s, <a
3603href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
3604href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
3605
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]3606<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
3607and therefore also a <a href="#Constant">Constant</a>. The value of the function
3608is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3609
3610<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3611<h4>
3612 <a name="m_Function">
3613 Important Public Members of the <tt>Function</tt> class
3614 </a>
3615</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3616
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3617<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3618
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3619<ul>
3620 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]3621 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3622
3623 <p>Constructor used when you need to create new <tt>Function</tt>s to add
3624 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]3625 create and what type of linkage the function should have. The <a
3626 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3627 specifies the formal arguments and return value for the function. The same
Duncan Sands8036ca42007-03-30 12:22:09 +0000[diff] [blame]3628 <a href="#FunctionType"><tt>FunctionType</tt></a> value can be used to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3629 create multiple functions. The <tt>Parent</tt> argument specifies the Module
3630 in which the function is defined. If this argument is provided, the function
3631 will automatically be inserted into that module's list of
3632 functions.</p></li>
3633
Chris Lattner62810e32008-11-25 18:34:50 +0000[diff] [blame]3634 <li><tt>bool isDeclaration()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3635
3636 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
3637 function is "external", it does not have a body, and thus must be resolved
3638 by linking with a function defined in a different translation unit.</p></li>
3639
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3640 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3641 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3642
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]3643 <tt>begin()</tt>, <tt>end()</tt>
3644 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3645
3646 <p>These are forwarding methods that make it easy to access the contents of
3647 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
3648 list.</p></li>
3649
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3650 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3651
3652 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
3653 is necessary to use when you need to update the list or perform a complex
3654 action that doesn't have a forwarding method.</p></li>
3655
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]3656 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3657iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]3658 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3659
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]3660 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]3661 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3662
3663 <p>These are forwarding methods that make it easy to access the contents of
3664 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
3665 list.</p></li>
3666
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3667 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3668
3669 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
3670 necessary to use when you need to update the list or perform a complex
3671 action that doesn't have a forwarding method.</p></li>
3672
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3673 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3674
3675 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
3676 function. Because the entry block for the function is always the first
3677 block, this returns the first block of the <tt>Function</tt>.</p></li>
3678
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3679 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
3680 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3681
3682 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
3683 <tt>Function</tt> and returns the return type of the function, or the <a
3684 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
3685 function.</p></li>
3686
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3687 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3688
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3689 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3690 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3691</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3692
3693</div>
3694
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3695</div>
3696
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3697<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3698<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3699 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3700</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3701
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3702<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3703
3704<p><tt>#include "<a
3705href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
3706<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]3707doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3708 Class</a><br>
3709Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
3710<a href="#Constant"><tt>Constant</tt></a>,
3711<a href="#User"><tt>User</tt></a>,
3712<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3713
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3714<p>Global variables are represented with the (surprise surprise)
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3715<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
3716subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
3717always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]3718"name" refers to their constant address). See
3719<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
3720variables may have an initial value (which must be a
3721<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
3722they may be marked as "constant" themselves (indicating that their contents
3723never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3724
3725<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3726<h4>
3727 <a name="m_GlobalVariable">
3728 Important Public Members of the <tt>GlobalVariable</tt> class
3729 </a>
3730</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3731
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3732<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3733
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3734<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3735 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
3736 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
3737 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
3738
3739 <p>Create a new global variable of the specified type. If
3740 <tt>isConstant</tt> is true then the global variable will be marked as
3741 unchanging for the program. The Linkage parameter specifies the type of
Duncan Sands667d4b82009-03-07 15:45:40 +0000[diff] [blame]3742 linkage (internal, external, weak, linkonce, appending) for the variable.
3743 If the linkage is InternalLinkage, WeakAnyLinkage, WeakODRLinkage,
3744 LinkOnceAnyLinkage or LinkOnceODRLinkage,&nbsp; then the resultant
3745 global variable will have internal linkage. AppendingLinkage concatenates
3746 together all instances (in different translation units) of the variable
3747 into a single variable but is only applicable to arrays. &nbsp;See
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3748 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
3749 further details on linkage types. Optionally an initializer, a name, and the
3750 module to put the variable into may be specified for the global variable as
3751 well.</p></li>
3752
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3753 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3754
3755 <p>Returns true if this is a global variable that is known not to
3756 be modified at runtime.</p></li>
3757
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3758 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3759
3760 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
3761
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3762 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3763
Benjamin Kramer8040cd32009-10-12 14:46:08 +0000[diff] [blame]3764 <p>Returns the initial value for a <tt>GlobalVariable</tt>. It is not legal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3765 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3766</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3767
3768</div>
3769
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3770</div>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3771
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3772<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3773<h3>
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3774 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3775</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3776
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3777<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3778
3779<p><tt>#include "<a
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3780href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
Stefanus Du Toit24e04112009-06-17 21:12:26 +0000[diff] [blame]3781doxygen info: <a href="/doxygen/classllvm_1_1BasicBlock.html">BasicBlock
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3782Class</a><br>
3783Superclass: <a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3784
Nick Lewyckyccd279d2011-02-17 02:19:22 +0000[diff] [blame]3785<p>This class represents a single entry single exit section of the code,
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3786commonly known as a basic block by the compiler community. The
3787<tt>BasicBlock</tt> class maintains a list of <a
3788href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
3789Matching the language definition, the last element of this list of instructions
3790is always a terminator instruction (a subclass of the <a
3791href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
3792
3793<p>In addition to tracking the list of instructions that make up the block, the
3794<tt>BasicBlock</tt> class also keeps track of the <a
3795href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
3796
3797<p>Note that <tt>BasicBlock</tt>s themselves are <a
3798href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
3799like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
3800<tt>label</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3801
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3802<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3803<h4>
3804 <a name="m_BasicBlock">
3805 Important Public Members of the <tt>BasicBlock</tt> class
3806 </a>
3807</h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3808
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3809<div>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3810<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3811
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3812<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
3813 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3814
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3815<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
3816insertion into a function. The constructor optionally takes a name for the new
3817block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
3818the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
3819automatically inserted at the end of the specified <a
3820href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
3821manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3822
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3823<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
3824<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
3825<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
3826<tt>size()</tt>, <tt>empty()</tt>
3827STL-style functions for accessing the instruction list.
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3828
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3829<p>These methods and typedefs are forwarding functions that have the same
3830semantics as the standard library methods of the same names. These methods
3831expose the underlying instruction list of a basic block in a way that is easy to
3832manipulate. To get the full complement of container operations (including
3833operations to update the list), you must use the <tt>getInstList()</tt>
3834method.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3835
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3836<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3837
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3838<p>This method is used to get access to the underlying container that actually
3839holds the Instructions. This method must be used when there isn't a forwarding
3840function in the <tt>BasicBlock</tt> class for the operation that you would like
3841to perform. Because there are no forwarding functions for "updating"
3842operations, you need to use this if you want to update the contents of a
3843<tt>BasicBlock</tt>.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3844
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3845<li><tt><a href="#Function">Function</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3846
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3847<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
3848embedded into, or a null pointer if it is homeless.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3849
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3850<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3851
Chris Lattner2b78d962007-02-03 20:02:25 +0000[diff] [blame]3852<p> Returns a pointer to the terminator instruction that appears at the end of
3853the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
3854instruction in the block is not a terminator, then a null pointer is
3855returned.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3856
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3857</ul>
3858
3859</div>
3860
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3861</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3862
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3863<!-- ======================================================================= -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3864<h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3865 <a name="Argument">The <tt>Argument</tt> class</a>
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]3866</h3>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3867
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3868<div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3869
3870<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]3871arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3872arguments. An argument has a pointer to the parent Function.</p>
3873
3874</div>
3875
NAKAMURA Takumif5af6ad2011-04-23 00:30:22 +0000[diff] [blame]3876</div>
3877
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]3878<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3879<hr>
3880<address>
3881 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]3882 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3883 <a href="http://validator.w3.org/check/referer"><img
Gabor Greifa9c0f2b2008-06-18 14:05:31 +0000[diff] [blame]3884 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]3885
3886 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
3887 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]3888 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]3889 Last modified: $Date$
3890</address>
3891
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]3892</body>
3893</html>