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