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4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
5 <title>The LLVM Lexicon</title>
6 <link rel="stylesheet" href="llvm.css" type="text/css">
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]7 <meta name="author" content="Various">
8 <meta name="description"
9 content="A glossary of terms used with the LLVM project.">
10</head>
11<body>
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]12<h1>The LLVM Lexicon</h1>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]13<p class="doc_warning">NOTE: This document is a work in progress!</p>
14<!-- *********************************************************************** -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]15<h2>Table Of Contents</h2>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]16<!-- *********************************************************************** -->
17<div class="doc_text">
18 <table>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]19 <tr><th colspan="8"><b>- <a href="#A">A</a> -</b></th></tr>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]20 <tr>
21 <td><a href="#ADCE">ADCE</a></td>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]22 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]23 <tr><th colspan="8"><b>- <a href="#B">B</a> -</b></th></tr>
Reid Spencer7c8d6582004-08-24 18:34:10 +0000[diff] [blame]24 <tr>
25 <td><a href="#BURS">BURS</a></td>
Reid Spencer7c8d6582004-08-24 18:34:10 +0000[diff] [blame]26 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]27 <tr><th colspan="8"><b>- <a href="#C">C</a> -</b></th></tr>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]28 <tr>
29 <td><a href="#CSE">CSE</a></td>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]30 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]31 <tr><th colspan="8"><b>- <a href="#D">D</a> -</b></th></tr>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]32 <tr>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]33 <td><a href="#DAG">DAG</a></td>
34 <td><a href="#Derived_Pointer">Derived Pointer</a></td>
Misha Brukmanadfa8b82004-09-05 03:00:20 +0000[diff] [blame]35 <td><a href="#DSA">DSA</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]36 <td><a href="#DSE">DSE</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]37 </tr>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]38 <tr><th colspan="8"><b>- <a href="#G">G</a> -</b></th></tr>
Dan Gohman8ef44982008-11-24 17:18:39 +0000[diff] [blame]39 <tr>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]40 <td><a href="#GC">GC</a></td>
41 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]42 <tr><th colspan="8"><b>- <a href="#I">I</a> -</b></th></tr>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]43 <tr>
44 <td><a href="#IPA">IPA</a></td>
45 <td><a href="#IPO">IPO</a></td>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]46 <td><a href="#ISel">ISel</a></td>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]47 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]48 <tr><th colspan="8"><b>- <a href="#L">L</a> -</b></th></tr>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]49 <tr>
Owen Anderson7a312482006-10-18 05:50:12 +0000[diff] [blame]50 <td><a href="#LCSSA">LCSSA</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]51 <td><a href="#LICM">LICM</a></td>
Misha Brukman2ace8cb2004-08-24 04:13:17 +0000[diff] [blame]52 <td><a href="#Load-VN">Load-VN</a></td>
Nick Lewyckya3c9f212010-04-05 05:48:47 +0000[diff] [blame]53 <td><a href="#LTO">LTO</a></td>
54 </tr>
55 <tr><th colspan="8"><b>- <a href="#M">M</a> -</b></th></tr>
56 <tr>
57 <td><a href="#MC">MC</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]58 </tr>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]59 <tr><th colspan="8"><b>- <a href="#O">O</a> -</b></th></tr>
60 <tr>
61 <td><a href="#Object_Pointer">Object Pointer</a></td>
62 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]63 <tr><th colspan="8"><b>- <a href="#P">P</a> -</b></th></tr>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]64 <tr>
65 <td><a href="#PRE">PRE</a></td>
Chris Lattner153827b2005-05-13 20:18:49 +0000[diff] [blame]66 </tr>
67 <tr><th colspan="8"><b>- <a href="#R">R</a> -</b></th></tr>
68 <tr>
Dan Gohman67feab32008-11-07 20:29:17 +0000[diff] [blame]69 <td><a href="#RAUW">RAUW</a></td>
Chris Lattner153827b2005-05-13 20:18:49 +0000[diff] [blame]70 <td><a href="#Reassociation">Reassociation</a></td>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]71 <td><a href="#Root">Root</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]72 </tr>
Reid Spencerc3c4c4f2004-11-01 08:19:36 +0000[diff] [blame]73 <tr><th colspan="8"><b>- <a href="#S">S</a> -</b></th></tr>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]74 <tr>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]75 <td><a href="#Safe_Point">Safe Point</a></td>
Chris Lattnera3198312005-11-29 01:34:50 +0000[diff] [blame]76 <td><a href="#SCC">SCC</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]77 <td><a href="#SCCP">SCCP</a></td>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]78 <td><a href="#SDISel">SDISel</a></td>
Chris Lattner4999a5c2006-02-08 16:59:49 +0000[diff] [blame]79 <td><a href="#SRoA">SRoA</a></td>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]80 <td><a href="#Stack_Map">Stack Map</a></td>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]81 </tr>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]82 </table>
83</div>
84
85<!-- *********************************************************************** -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]86<h2>Definitions</h2>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]87<!-- *********************************************************************** -->
88<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]89<h3><a name="A">- A -</a></h3>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]90<div class="doc_text">
91 <dl>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]92 <dt><a name="ADCE"><b>ADCE</b></a></dt>
93 <dd>Aggressive Dead Code Elimination</dd>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]94 </dl>
95</div>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]96<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]97<h3><a name="B">- B -</a></h3>
Reid Spencer7c8d6582004-08-24 18:34:10 +0000[diff] [blame]98<div class="doc_text">
99 <dl>
100 <dt><a name="BURS"><b>BURS</b></a></dt>
Bill Wendling94d371b2008-07-22 06:46:17 +0000[diff] [blame]101 <dd>Bottom Up Rewriting System&mdash;A method of instruction selection for
Chris Lattner7bf499c2004-08-24 18:53:39 +0000[diff] [blame]102 code generation. An example is the <a
103href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
Reid Spencer7c8d6582004-08-24 18:34:10 +0000[diff] [blame]104 </dl>
105</div>
106<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]107<h3><a name="C">- C -</a></h3>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]108<div class="doc_text">
109 <dl>
110 <dt><a name="CSE"><b>CSE</b></a></dt>
111 <dd>Common Subexpression Elimination. An optimization that removes common
112 subexpression compuation. For example <tt>(a+b)*(a+b)</tt> has two
113 subexpressions that are the same: <tt>(a+b)</tt>. This optimization would
114 perform the addition only once and then perform the multiply (but only if
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]115 it's compulationally correct/safe).
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]116 </dl>
117</div>
118<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]119<h3><a name="D">- D -</a></h3>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]120<div class="doc_text">
121 <dl>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]122 <dt><a name="DAG"><b>DAG</b></a></dt>
123 <dd>Directed Acyclic Graph</dd>
124 <dt><a name="Derived_Pointer"><b>Derived Pointer</b></a></dt>
125 <dd>A pointer to the interior of an object, such that a garbage collector
126 is unable to use the pointer for reachability analysis. While a derived
127 pointer is live, the corresponding object pointer must be kept in a root,
128 otherwise the collector might free the referenced object. With copying
129 collectors, derived pointers pose an additional hazard that they may be
130 invalidated at any <a href="Safe_Point">safe point</a>. This term is used in
131 opposition to <a href="#Object_Pointer">object pointer</a>.</dd>
Misha Brukmanadfa8b82004-09-05 03:00:20 +0000[diff] [blame]132 <dt><a name="DSA"><b>DSA</b></a></dt>
Misha Brukman0d68e4c2004-09-05 03:57:23 +0000[diff] [blame]133 <dd>Data Structure Analysis</dd>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]134 <dt><a name="DSE"><b>DSE</b></a></dt>
135 <dd>Dead Store Elimination</dd>
136 </dl>
137</div>
138<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]139<h3><a name="G">- G -</a></h3>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]140<div class="doc_text">
141 <dl>
142 <dt><a name="GC"><b>GC</b></a></dt>
143 <dd>Garbage Collection. The practice of using reachability analysis instead
144 of explicit memory management to reclaim unused memory.</dd>
145 </dl>
146</div>
147<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]148<h3><a name="H">- H -</a></h3>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]149<div class="doc_text">
150 <dl>
151 <dt><a name="Heap"><b>Heap</b></a></dt>
152 <dd>In garbage collection, the region of memory which is managed using
153 reachability analysis.</dd>
154 </dl>
155</div>
156<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]157<h3><a name="I">- I -</a></h3>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]158<div class="doc_text">
159 <dl>
160 <dt><a name="IPA"><b>IPA</b></a></dt>
161 <dd>Inter-Procedural Analysis. Refers to any variety of code analysis that
162 occurs between procedures, functions or compilation units (modules).</dd>
163 <dt><a name="IPO"><b>IPO</b></a></dt>
164 <dd>Inter-Procedural Optimization. Refers to any variety of code
165 optimization that occurs between procedures, functions or compilation units
166 (modules).</dd>
Torok Edwin7b747ef2008-10-28 16:54:34 +0000[diff] [blame]167 <dt><a name="ISel"><b>ISel</b></a></dt>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]168 <dd>Instruction Selection.</dd>
Reid Spencer965ff462004-10-30 21:40:28 +0000[diff] [blame]169 </dl>
170</div>
171<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]172<h3><a name="L">- L -</a></h3>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]173<div class="doc_text">
174 <dl>
Nick Lewyckya3c9f212010-04-05 05:48:47 +0000[diff] [blame]175 <dt><a name="LCSSA"><b>LCSSA</b></a></dt>
176 <dd>Loop-Closed Static Single Assignment Form</dd>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]177 <dt><a name="LICM"><b>LICM</b></a></dt>
178 <dd>Loop Invariant Code Motion</dd>
Misha Brukman2ace8cb2004-08-24 04:13:17 +0000[diff] [blame]179 <dt><a name="Load-VN"><b>Load-VN</b></a></dt>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]180 <dd>Load Value Numbering</dd>
Nick Lewyckya3c9f212010-04-05 05:48:47 +0000[diff] [blame]181 <dt><a name="LTO"><b>LTO</b></a></dt>
182 <dd>Link-Time Optimization</dd>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]183 </dl>
184</div>
Nick Lewyckya3c9f212010-04-05 05:48:47 +0000[diff] [blame]185<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]186<h3><a name="M">- M -</a></h3>
Nick Lewyckya3c9f212010-04-05 05:48:47 +0000[diff] [blame]187<div class="doc_text">
188 <dl>
189 <dt><a name="MC"><b>MC</b></a></dt>
190 <dd>Machine Code</dd>
191 </dl>
192</div>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]193<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]194<h3><a name="O">- O -</a></h3>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]195<div class="doc_text">
196 <dl>
197 <dt><a name="Object_Pointer"><b>Object Pointer</b></a></dt>
198 <dd>A pointer to an object such that the garbage collector is able to trace
199 references contained within the object. This term is used in opposition to
200 <a href="#Derived_Pointer">derived pointer</a>.</dd>
201 </dl>
202</div>
203
204<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]205<h3><a name="P">- P -</a></h3>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]206<div class="doc_text">
207 <dl>
208 <dt><a name="PRE"><b>PRE</b></a></dt>
209 <dd>Partial Redundancy Elimination</dd>
210 </dl>
211</div>
Chris Lattner153827b2005-05-13 20:18:49 +0000[diff] [blame]212
213<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]214<h3><a name="R">- R -</a></h3>
Chris Lattner153827b2005-05-13 20:18:49 +0000[diff] [blame]215<div class="doc_text">
216 <dl>
Dan Gohman67feab32008-11-07 20:29:17 +0000[diff] [blame]217 <dt><a name="RAUW"><b>RAUW</b></a></dt> <dd>An abbreviation for Replace
218 All Uses With. The functions User::replaceUsesOfWith(),
219 Value::replaceAllUsesWith(), and Constant::replaceUsesOfWithOnConstant()
220 implement the replacement of one Value with another by iterating over its
221 def/use chain and fixing up all of the pointers to point to the new value.
222 See also <a href="ProgrammersManual.html#iterate_chains">def/use chains</a>.
223 </dd>
Chris Lattner153827b2005-05-13 20:18:49 +0000[diff] [blame]224 <dt><a name="Reassociation"><b>Reassociation</b></a></dt> <dd>Rearranging
225 associative expressions to promote better redundancy elimination and other
226 optimization. For example, changing (A+B-A) into (B+A-A), permitting it to
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]227 be optimized into (B+0) then (B).</dd>
228 <dt><a name="Root"><b>Root</b></a></dt> <dd>In garbage collection, a
229 pointer variable lying outside of the <a href="#Heap">heap</a> from which
230 the collector begins its reachability analysis. In the context of code
Misha Brukmane10a3d52008-12-14 08:01:51 +0000[diff] [blame]231 generation, "root" almost always refers to a "stack root" -- a local or
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]232 temporary variable within an executing function.</dd>
Chris Lattner153827b2005-05-13 20:18:49 +0000[diff] [blame]233 </dl>
234</div>
235
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]236<!-- _______________________________________________________________________ -->
NAKAMURA Takumifc8d9302011-04-18 23:59:50 +0000[diff] [blame^]237<h3><a name="S">- S -</a></h3>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]238<div class="doc_text">
239 <dl>
Torok Edwin7b747ef2008-10-28 16:54:34 +0000[diff] [blame]240 <dt><a name="Safe_Point"><b>Safe Point</b></a></dt>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]241 <dd>In garbage collection, it is necessary to identify <a href="#Root">stack
242 roots</a> so that reachability analysis may proceed. It may be infeasible to
243 provide this information for every instruction, so instead the information
244 may is calculated only at designated safe points. With a copying collector,
245 <a href="#Derived_Pointers">derived pointers</a> must not be retained across
246 safe points and <a href="#Object_Pointers">object pointers</a> must be
247 reloaded from stack roots.</dd>
248 <dt><a name="SDISel"><b>SDISel</b></a></dt>
249 <dd>Selection DAG Instruction Selection.</dd>
Chris Lattnera3198312005-11-29 01:34:50 +0000[diff] [blame]250 <dt><a name="SCC"><b>SCC</b></a></dt>
251 <dd>Strongly Connected Component</dd>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]252 <dt><a name="SCCP"><b>SCCP</b></a></dt>
Chris Lattnera3198312005-11-29 01:34:50 +0000[diff] [blame]253 <dd>Sparse Conditional Constant Propagation</dd>
Chris Lattner4999a5c2006-02-08 16:59:49 +0000[diff] [blame]254 <dt><a name="SRoA"><b>SRoA</b></a></dt>
255 <dd>Scalar Replacement of Aggregates</dd>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]256 <dt><a name="SSA"><b>SSA</b></a></dt>
257 <dd>Static Single Assignment</dd>
Gordon Henriksen0076a672007-09-27 19:31:36 +0000[diff] [blame]258 <dt><a name="Stack_Map"><b>Stack Map</b></a></dt>
259 <dd>In garbage collection, metadata emitted by the code generator which
260 identifies <a href="#Root">roots</a> within the stack frame of an executing
261 function.</dd>
Misha Brukman00b21ae2004-08-24 01:57:02 +0000[diff] [blame]262 </dl>
263</div>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]264<!-- *********************************************************************** -->
265<hr>
266<address> <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
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Reid Spencerca058542006-03-14 05:39:39 +0000[diff] [blame]270 href="http://llvm.org/">The LLVM Team</a><br>
NAKAMURA Takumica46f5a2011-04-09 02:13:37 +0000[diff] [blame]271<a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Reid Spencer9f093ed2004-08-17 09:38:50 +0000[diff] [blame]272Last modified: $Date$
273</address>
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