GarbageCollection.html is expanded to encompass the coming

capabilities. This is a major rewrite and is easier to read en toto
rather than patchwise.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42414 91177308-0d34-0410-b5e6-96231b3b80d8

docs/Lexicon.html

@@ -30,13 +30,19 @@
     </tr>
     <tr><th colspan="8"><b>- <a href="#D">D</a> -</b></th></tr>
     <tr>
+      <td><a href="#DAG">DAG</a></td>
+      <td><a href="#Derived_Pointer">Derived Pointer</a></td>
       <td><a href="#DSA">DSA</a></td>
       <td><a href="#DSE">DSE</a></td>
     </tr>
+    <tr><th colspan="8"><b>- <a href="#G">G</a> -</b></th></tr>
+      <td><a href="#GC">GC</a></td>
+    </tr>
     <tr><th colspan="8"><b>- <a href="#I">I</a> -</b></th></tr>
     <tr>
       <td><a href="#IPA">IPA</a></td>
       <td><a href="#IPO">IPO</a></td>
+      <td><a href="#ISel">ISel</a></td>
     </tr>
     <tr><th colspan="8"><b>- <a href="#L">L</a> -</b></th></tr>
     <tr>
@@ -44,6 +50,10 @@
       <td><a href="#LICM">LICM</a></td>
       <td><a href="#Load-VN">Load-VN</a></td>
     </tr>
+    <tr><th colspan="8"><b>- <a href="#O">O</a> -</b></th></tr>
+    <tr>
+      <td><a href="#Object_Pointer">Object Pointer</a></td>
+    </tr>
     <tr><th colspan="8"><b>- <a href="#P">P</a> -</b></th></tr>
     <tr>
       <td><a href="#PRE">PRE</a></td>
@@ -51,13 +61,16 @@
     <tr><th colspan="8"><b>- <a href="#R">R</a> -</b></th></tr>
     <tr>
       <td><a href="#Reassociation">Reassociation</a></td>
+      <td><a href="#Root">Root</a></td>
     </tr>
     <tr><th colspan="8"><b>- <a href="#S">S</a> -</b></th></tr>
     <tr>
+      <td><a href="#Safe_Point">Safe Point</a></td>
       <td><a href="#SCC">SCC</a></td>
       <td><a href="#SCCP">SCCP</a></td>
+      <td><a href="#SDISel">SDISel</a></td>
       <td><a href="#SRoA">SRoA</a></td>
-      <td><a href="#SSA">SSA</a></td>
+      <td><a href="#Stack_Map">Stack Map</a></td>
     </tr>
   </table>
 </div>
@@ -92,13 +105,23 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
     subexpression compuation. For example <tt>(a+b)*(a+b)</tt> has two
     subexpressions that are the same: <tt>(a+b)</tt>. This optimization would
     perform the addition only once and then perform the multiply (but only if
-    its compulationally correct/safe).
+    it's compulationally correct/safe).
   </dl>
 </div>
 <!-- _______________________________________________________________________ -->
 <div class="doc_subsection"><a name="D">- D -</a></div>
 <div class="doc_text">
   <dl>
+    <dt><a name="DAG"><b>DAG</b></a></dt>
+    <dd>Directed Acyclic Graph</dd>
+    <dt><a name="Derived_Pointer"><b>Derived Pointer</b></a></dt>
+    <dd>A pointer to the interior of an object, such that a garbage collector
+    is unable to use the pointer for reachability analysis. While a derived
+    pointer is live, the corresponding object pointer must be kept in a root,
+    otherwise the collector might free the referenced object. With copying
+    collectors, derived pointers pose an additional hazard that they may be
+    invalidated at any <a href="Safe_Point">safe point</a>. This term is used in
+    opposition to <a href="#Object_Pointer">object pointer</a>.</dd>
     <dt><a name="DSA"><b>DSA</b></a></dt>
     <dd>Data Structure Analysis</dd>
     <dt><a name="DSE"><b>DSE</b></a></dt>
@@ -106,6 +129,24 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
   </dl>
 </div>
 <!-- _______________________________________________________________________ -->
+<div class="doc_subsection"><a name="G">- G -</a></div>
+<div class="doc_text">
+  <dl>
+    <dt><a name="GC"><b>GC</b></a></dt>
+    <dd>Garbage Collection. The practice of using reachability analysis instead
+    of explicit memory management to reclaim unused memory.</dd>
+  </dl>
+</div>
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsection"><a name="H">- H -</a></div>
+<div class="doc_text">
+  <dl>
+    <dt><a name="Heap"><b>Heap</b></a></dt>
+    <dd>In garbage collection, the region of memory which is managed using
+    reachability analysis.</dd>
+  </dl>
+</div>
+<!-- _______________________________________________________________________ -->
 <div class="doc_subsection"><a name="I">- I -</a></div>
 <div class="doc_text">
   <dl>
@@ -116,6 +157,8 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
     <dd>Inter-Procedural Optimization. Refers to any variety of code
     optimization that occurs between procedures, functions or compilation units
     (modules).</dd>
+    <dt><a name="IPO"><b>ISel</b></a></dt>
+    <dd>Instruction Selection.</dd>
   </dl>
 </div>
 <!-- _______________________________________________________________________ -->
@@ -131,6 +174,17 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
   </dl>
 </div>
 
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsection"><a name="P">- O -</a></div>
+<div class="doc_text">
+  <dl>
+    <dt><a name="Object_Pointer"><b>Object Pointer</b></a></dt>
+    <dd>A pointer to an object such that the garbage collector is able to trace
+    references contained within the object. This term is used in opposition to
+    <a href="#Derived_Pointer">derived pointer</a>.</dd>
+  </dl>
+</div>
+
 <!-- _______________________________________________________________________ -->
 <div class="doc_subsection"><a name="P">- P -</a></div>
 <div class="doc_text">
@@ -147,7 +201,12 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
     <dt><a name="Reassociation"><b>Reassociation</b></a></dt> <dd>Rearranging
     associative expressions to promote better redundancy elimination and other
     optimization.  For example, changing (A+B-A) into (B+A-A), permitting it to
-    be optimized into (B+0) then (B).
+    be optimized into (B+0) then (B).</dd>
+    <dt><a name="Root"><b>Root</b></a></dt> <dd>In garbage collection, a
+    pointer variable lying outside of the <a href="#Heap">heap</a> from which
+    the collector begins its reachability analysis. In the context of code
+    generation, "root" almost always refers to a "stack root"&#151;a local or
+    temporary variable within an executing function.</dd>
   </dl>
 </div>
 
@@ -155,6 +214,16 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
 <div class="doc_subsection"><a name="S">- S -</a></div>
 <div class="doc_text">
   <dl>
+    <dt><a name="SCC"><b>Safe Point</b></a></dt>
+    <dd>In garbage collection, it is necessary to identify <a href="#Root">stack
+    roots</a> so that reachability analysis may proceed. It may be infeasible to
+    provide this information for every instruction, so instead the information
+    may is calculated only at designated safe points. With a copying collector,
+    <a href="#Derived_Pointers">derived pointers</a> must not be retained across
+    safe points and <a href="#Object_Pointers">object pointers</a> must be
+    reloaded from stack roots.</dd>
+    <dt><a name="SDISel"><b>SDISel</b></a></dt>
+    <dd>Selection DAG Instruction Selection.</dd>
     <dt><a name="SCC"><b>SCC</b></a></dt>
     <dd>Strongly Connected Component</dd>
     <dt><a name="SCCP"><b>SCCP</b></a></dt>
@@ -163,6 +232,10 @@ href="http://www.program-transformation.org/Transform/BURG">BURG</a> tool.</dd>
     <dd>Scalar Replacement of Aggregates</dd>
     <dt><a name="SSA"><b>SSA</b></a></dt>
     <dd>Static Single Assignment</dd>
+    <dt><a name="Stack_Map"><b>Stack Map</b></a></dt>
+    <dd>In garbage collection, metadata emitted by the code generator which
+    identifies <a href="#Root">roots</a> within the stack frame of an executing
+    function.</dd>
   </dl>
 </div>
 <!-- *********************************************************************** -->

docs/llvm.css

@@ -13,7 +13,7 @@ address     { clear: right; }
 
 TR, TD      { border: 2px solid gray; padding: 4pt 4pt 2pt 2pt; }
 TH          { border: 2px solid gray; font-weight: bold; font-size: 105%; 
-              color: black; background: url("img/lines.gif");
+              background: url("img/lines.gif");
               font-family: "Georgia,Palatino,Times,Roman,SanSerif"; text-align:center;
               vertical-align: middle; }
 TABLE       { text-align: center; border: 2px solid black; 

runtime/GC/SemiSpace/README.txt

@@ -0,0 +1,5 @@
+//===----------------------------------------------------------------------===//
+
+Possible enhancement: If a collection cycle happens and the heap is not
+compacted very much (say less than 25% of the allocated memory was freed), the
+memory regions should be doubled in size.