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gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / 624dc1d4abf26a3ccd474f85a39058a99a9053ca / . / docs / Lexicon.html
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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 Spencer85baf762004-08-17 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 Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]12<h1>The LLVM Lexicon</h1>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]13<p class="doc_warning">NOTE: This document is a work in progress!</p>
14<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]15<h2>Table Of Contents</h2>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]16<!-- *********************************************************************** -->
17<div class="doc_text">
18 <table>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]19 <tr><th colspan="8"><b>- <a href="#A">A</a> -</b></th></tr>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]20 <tr>
21 <td><a href="#ADCE">ADCE</a></td>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]22 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]23 <tr><th colspan="8"><b>- <a href="#B">B</a> -</b></th></tr>
Reid Spencerce6be332004-08-24 18:34:10 +0000[diff] [blame]24 <tr>
25 <td><a href="#BURS">BURS</a></td>
Reid Spencerce6be332004-08-24 18:34:10 +0000[diff] [blame]26 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]27 <tr><th colspan="8"><b>- <a href="#C">C</a> -</b></th></tr>
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]28 <tr>
29 <td><a href="#CSE">CSE</a></td>
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]30 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]31 <tr><th colspan="8"><b>- <a href="#D">D</a> -</b></th></tr>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]32 <tr>
Gordon Henriksen326e24f2007-09-27 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 Brukman9a4c9042004-09-05 03:00:20 +0000[diff] [blame]35 <td><a href="#DSA">DSA</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]36 <td><a href="#DSE">DSE</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]37 </tr>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]38 <tr><th colspan="8"><b>- <a href="#G">G</a> -</b></th></tr>
Dan Gohmanf0032762008-11-24 17:18:39 +0000[diff] [blame]39 <tr>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]40 <td><a href="#GC">GC</a></td>
41 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]42 <tr><th colspan="8"><b>- <a href="#I">I</a> -</b></th></tr>
Reid Spencera07e0b52004-10-30 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 Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]46 <td><a href="#ISel">ISel</a></td>
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]47 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]48 <tr><th colspan="8"><b>- <a href="#L">L</a> -</b></th></tr>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]49 <tr>
Owen Andersona6fc5012006-10-18 05:50:12 +0000[diff] [blame]50 <td><a href="#LCSSA">LCSSA</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]51 <td><a href="#LICM">LICM</a></td>
Misha Brukman183cfc22004-08-24 04:13:17 +0000[diff] [blame]52 <td><a href="#Load-VN">Load-VN</a></td>
Nick Lewycky00759c12010-04-05 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]58 </tr>
Gordon Henriksen326e24f2007-09-27 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 Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]63 <tr><th colspan="8"><b>- <a href="#P">P</a> -</b></th></tr>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]64 <tr>
65 <td><a href="#PRE">PRE</a></td>
Chris Lattnerdbb85852005-05-13 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 Gohmanc4479a72008-11-07 20:29:17 +0000[diff] [blame]69 <td><a href="#RAUW">RAUW</a></td>
Chris Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]70 <td><a href="#Reassociation">Reassociation</a></td>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]71 <td><a href="#Root">Root</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]72 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]73 <tr><th colspan="8"><b>- <a href="#S">S</a> -</b></th></tr>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]74 <tr>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]75 <td><a href="#Safe_Point">Safe Point</a></td>
Chris Lattner59f7f212005-11-29 01:34:50 +0000[diff] [blame]76 <td><a href="#SCC">SCC</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]77 <td><a href="#SCCP">SCCP</a></td>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]78 <td><a href="#SDISel">SDISel</a></td>
Chris Lattnered51a0f2006-02-08 16:59:49 +0000[diff] [blame]79 <td><a href="#SRoA">SRoA</a></td>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]80 <td><a href="#Stack_Map">Stack Map</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]81 </tr>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]82 </table>
83</div>
84
85<!-- *********************************************************************** -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]86<h2>Definitions</h2>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]87<!-- *********************************************************************** -->
88<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]89<h3><a name="A">- A -</a></h3>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]90<div class="doc_text">
91 <dl>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]92 <dt><a name="ADCE"><b>ADCE</b></a></dt>
93 <dd>Aggressive Dead Code Elimination</dd>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]94 </dl>
95</div>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]96<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]97<h3><a name="B">- B -</a></h3>
Reid Spencerce6be332004-08-24 18:34:10 +0000[diff] [blame]98<div class="doc_text">
99 <dl>
100 <dt><a name="BURS"><b>BURS</b></a></dt>
Bill Wendling7c6d4102008-07-22 06:46:17 +0000[diff] [blame]101 <dd>Bottom Up Rewriting System&mdash;A method of instruction selection for
Chris Lattnerc4985ba2004-08-24 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 Spencerce6be332004-08-24 18:34:10 +0000[diff] [blame]104 </dl>
105</div>
106<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]107<h3><a name="C">- C -</a></h3>
Reid Spencera07e0b52004-10-30 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 Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]115 it's compulationally correct/safe).
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]116 </dl>
117</div>
118<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]119<h3><a name="D">- D -</a></h3>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]120<div class="doc_text">
121 <dl>
Gordon Henriksen326e24f2007-09-27 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 Brukman9a4c9042004-09-05 03:00:20 +0000[diff] [blame]132 <dt><a name="DSA"><b>DSA</b></a></dt>
Misha Brukman100bd712004-09-05 03:57:23 +0000[diff] [blame]133 <dd>Data Structure Analysis</dd>
Misha Brukmanec8fe3c2004-08-24 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 Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]139<h3><a name="G">- G -</a></h3>
Gordon Henriksen326e24f2007-09-27 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 Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]148<h3><a name="H">- H -</a></h3>
Gordon Henriksen326e24f2007-09-27 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 Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]157<h3><a name="I">- I -</a></h3>
Reid Spencera07e0b52004-10-30 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 Edwin2b9cbf12008-10-28 16:54:34 +0000[diff] [blame]167 <dt><a name="ISel"><b>ISel</b></a></dt>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]168 <dd>Instruction Selection.</dd>
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]169 </dl>
170</div>
171<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]172<h3><a name="L">- L -</a></h3>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]173<div class="doc_text">
174 <dl>
Nick Lewycky00759c12010-04-05 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]177 <dt><a name="LICM"><b>LICM</b></a></dt>
178 <dd>Loop Invariant Code Motion</dd>
Misha Brukman183cfc22004-08-24 04:13:17 +0000[diff] [blame]179 <dt><a name="Load-VN"><b>Load-VN</b></a></dt>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]180 <dd>Load Value Numbering</dd>
Nick Lewycky00759c12010-04-05 05:48:47 +0000[diff] [blame]181 <dt><a name="LTO"><b>LTO</b></a></dt>
182 <dd>Link-Time Optimization</dd>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]183 </dl>
184</div>
Nick Lewycky00759c12010-04-05 05:48:47 +0000[diff] [blame]185<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]186<h3><a name="M">- M -</a></h3>
Nick Lewycky00759c12010-04-05 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]193<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]194<h3><a name="O">- O -</a></h3>
Gordon Henriksen326e24f2007-09-27 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 Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]205<h3><a name="P">- P -</a></h3>
Misha Brukmanec8fe3c2004-08-24 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 Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]212
213<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]214<h3><a name="R">- R -</a></h3>
Chris Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]215<div class="doc_text">
216 <dl>
Dan Gohmanc4479a72008-11-07 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 Lattnerdbb85852005-05-13 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 Henriksen326e24f2007-09-27 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 Brukman3c8da592008-12-14 08:01:51 +0000[diff] [blame]231 generation, "root" almost always refers to a "stack root" -- a local or
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]232 temporary variable within an executing function.</dd>
Chris Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]233 </dl>
234</div>
235
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]236<!-- _______________________________________________________________________ -->
NAKAMURA Takumi05d02652011-04-18 23:59:50 +0000[diff] [blame]237<h3><a name="S">- S -</a></h3>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]238<div class="doc_text">
239 <dl>
Torok Edwin2b9cbf12008-10-28 16:54:34 +0000[diff] [blame]240 <dt><a name="Safe_Point"><b>Safe Point</b></a></dt>
Gordon Henriksen326e24f2007-09-27 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 Lattner59f7f212005-11-29 01:34:50 +0000[diff] [blame]250 <dt><a name="SCC"><b>SCC</b></a></dt>
251 <dd>Strongly Connected Component</dd>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]252 <dt><a name="SCCP"><b>SCCP</b></a></dt>
Chris Lattner59f7f212005-11-29 01:34:50 +0000[diff] [blame]253 <dd>Sparse Conditional Constant Propagation</dd>
Chris Lattnered51a0f2006-02-08 16:59:49 +0000[diff] [blame]254 <dt><a name="SRoA"><b>SRoA</b></a></dt>
255 <dd>Scalar Replacement of Aggregates</dd>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]256 <dt><a name="SSA"><b>SSA</b></a></dt>
257 <dd>Static Single Assignment</dd>
Gordon Henriksen326e24f2007-09-27 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]262 </dl>
263</div>
Reid Spencer85baf762004-08-17 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 Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]270 href="http://llvm.org/">The LLVM Team</a><br>
NAKAMURA Takumib9a33632011-04-09 02:13:37 +0000[diff] [blame]271<a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]272Last modified: $Date$
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