Gitiles
Code Review Sign In
gerrit-public.fairphone.software / fp2-dev / platform / external / llvm / c500566d9fb70472a17f62b4cf1689062c52e095 / . / docs / Lexicon.html
blob: 820fdd6f022b91a42ecdb3e0d702cb19ff982dbe [file] [log] [blame]
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
2<html>
3<head>
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>
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 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>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]53 </tr>
Gordon Henriksen326e24f2007-09-27 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 Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]58 <tr><th colspan="8"><b>- <a href="#P">P</a> -</b></th></tr>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]59 <tr>
60 <td><a href="#PRE">PRE</a></td>
Chris Lattnerdbb85852005-05-13 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 Gohmanc4479a72008-11-07 20:29:17 +0000[diff] [blame]64 <td><a href="#RAUW">RAUW</a></td>
Chris Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]65 <td><a href="#Reassociation">Reassociation</a></td>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]66 <td><a href="#Root">Root</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]67 </tr>
Reid Spencerd3f876c2004-11-01 08:19:36 +0000[diff] [blame]68 <tr><th colspan="8"><b>- <a href="#S">S</a> -</b></th></tr>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]69 <tr>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]70 <td><a href="#Safe_Point">Safe Point</a></td>
Chris Lattner59f7f212005-11-29 01:34:50 +0000[diff] [blame]71 <td><a href="#SCC">SCC</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]72 <td><a href="#SCCP">SCCP</a></td>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]73 <td><a href="#SDISel">SDISel</a></td>
Chris Lattnered51a0f2006-02-08 16:59:49 +0000[diff] [blame]74 <td><a href="#SRoA">SRoA</a></td>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]75 <td><a href="#Stack_Map">Stack Map</a></td>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]76 </tr>
Reid Spencer85baf762004-08-17 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]87 <dt><a name="ADCE"><b>ADCE</b></a></dt>
88 <dd>Aggressive Dead Code Elimination</dd>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]89 </dl>
90</div>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]91<!-- _______________________________________________________________________ -->
Reid Spencerce6be332004-08-24 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 Wendling7c6d4102008-07-22 06:46:17 +0000[diff] [blame]96 <dd>Bottom Up Rewriting System&mdash;A method of instruction selection for
Chris Lattnerc4985ba2004-08-24 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 Spencerce6be332004-08-24 18:34:10 +0000[diff] [blame]99 </dl>
100</div>
101<!-- _______________________________________________________________________ -->
Reid Spencera07e0b52004-10-30 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 Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]110 it's compulationally correct/safe).
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]111 </dl>
112</div>
113<!-- _______________________________________________________________________ -->
Misha Brukmanec8fe3c2004-08-24 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 Henriksen326e24f2007-09-27 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 Brukman9a4c9042004-09-05 03:00:20 +0000[diff] [blame]127 <dt><a name="DSA"><b>DSA</b></a></dt>
Misha Brukman100bd712004-09-05 03:57:23 +0000[diff] [blame]128 <dd>Data Structure Analysis</dd>
Misha Brukmanec8fe3c2004-08-24 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 Henriksen326e24f2007-09-27 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 Spencera07e0b52004-10-30 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 Edwin2b9cbf12008-10-28 16:54:34 +0000[diff] [blame]162 <dt><a name="ISel"><b>ISel</b></a></dt>
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]163 <dd>Instruction Selection.</dd>
Reid Spencera07e0b52004-10-30 21:40:28 +0000[diff] [blame]164 </dl>
165</div>
166<!-- _______________________________________________________________________ -->
Misha Brukmanec8fe3c2004-08-24 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 Andersona6fc5012006-10-18 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]172 <dt><a name="LICM"><b>LICM</b></a></dt>
173 <dd>Loop Invariant Code Motion</dd>
Misha Brukman183cfc22004-08-24 04:13:17 +0000[diff] [blame]174 <dt><a name="Load-VN"><b>Load-VN</b></a></dt>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]175 <dd>Load Value Numbering</dd>
176 </dl>
177</div>
Chris Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]178
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]179<!-- _______________________________________________________________________ -->
Torok Edwin2b9cbf12008-10-28 16:54:34 +0000[diff] [blame]180<div class="doc_subsection"><a name="O">- O -</a></div>
Gordon Henriksen326e24f2007-09-27 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 Brukmanec8fe3c2004-08-24 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 Lattnerdbb85852005-05-13 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 Gohmanc4479a72008-11-07 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 Lattnerdbb85852005-05-13 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 Henriksen326e24f2007-09-27 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 Brukman3c8da592008-12-14 08:01:51 +0000[diff] [blame]217 generation, "root" almost always refers to a "stack root" -- a local or
Gordon Henriksen326e24f2007-09-27 19:31:36 +0000[diff] [blame]218 temporary variable within an executing function.</dd>
Chris Lattnerdbb85852005-05-13 20:18:49 +0000[diff] [blame]219 </dl>
220</div>
221
Misha Brukmanec8fe3c2004-08-24 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 Edwin2b9cbf12008-10-28 16:54:34 +0000[diff] [blame]226 <dt><a name="Safe_Point"><b>Safe Point</b></a></dt>
Gordon Henriksen326e24f2007-09-27 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 Lattner59f7f212005-11-29 01:34:50 +0000[diff] [blame]236 <dt><a name="SCC"><b>SCC</b></a></dt>
237 <dd>Strongly Connected Component</dd>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]238 <dt><a name="SCCP"><b>SCCP</b></a></dt>
Chris Lattner59f7f212005-11-29 01:34:50 +0000[diff] [blame]239 <dd>Sparse Conditional Constant Propagation</dd>
Chris Lattnered51a0f2006-02-08 16:59:49 +0000[diff] [blame]240 <dt><a name="SRoA"><b>SRoA</b></a></dt>
241 <dd>Scalar Replacement of Aggregates</dd>
Misha Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]242 <dt><a name="SSA"><b>SSA</b></a></dt>
243 <dd>Static Single Assignment</dd>
Gordon Henriksen326e24f2007-09-27 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 Brukmanec8fe3c2004-08-24 01:57:02 +0000[diff] [blame]248 </dl>
249</div>
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]250<!-- *********************************************************************** -->
251<hr>
252<address> <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]253 src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a><a
Reid Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]254 href="http://validator.w3.org/check/referer"><img
Misha Brukman44408702008-12-11 17:34:48 +0000[diff] [blame]255 src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a><a
Reid Spencer05fe4b02006-03-14 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 Spencer85baf762004-08-17 09:38:50 +0000[diff] [blame]258Last modified: $Date$
259</address>
260<!-- vim: sw=2
261-->
262</body>
263</html>