-<!-- *********************************************************************** -->
-
-<div class="doc_text">
-
-<p>Implementing a garbage collector for LLVM is fairly straightforward. The
-LLVM garbage collectors are provided in a form that makes them easy to link into
-the language-specific runtime that a language front-end would use. They require
-functionality from the language-specific runtime to get information about <a
-href="#gcdescriptors">where pointers are located in heap objects</a>.</p>
-
-<p>The implementation must include the
-<a href="#allocate"><tt>llvm_gc_allocate</tt></a> and
-<a href="#explicit"><tt>llvm_gc_collect</tt></a> functions. To do this, it will
-probably have to <a href="#traceroots">trace through the roots
-from the stack</a> and understand the <a href="#gcdescriptors">GC descriptors
-for heap objects</a>. Luckily, there are some <a href="#usage">example
-implementations</a> available.
-</p>
-</div>
-
-
-<!-- ======================================================================= -->
-<div class="doc_subsection">
- <a name="gcdescriptors">Tracing GC pointers from heap objects</a>
-</div>
-
-<div class="doc_text">
-<p>
-The three most common ways to keep track of where pointers live in heap objects
-are (listed in order of space overhead required):</p>
-
-<ol>
-<li>In languages with polymorphic objects, pointers from an object header are
-usually used to identify the GC pointers in the heap object. This is common for
-object-oriented languages like Self, Smalltalk, Java, or C#.</li>
-
-<li>If heap objects are not polymorphic, often the "shape" of the heap can be
-determined from the roots of the heap or from some other meta-data [<a
-href="#appel89">Appel89</a>, <a href="#goldberg91">Goldberg91</a>, <a
-href="#tolmach94">Tolmach94</a>]. In this case, the garbage collector can
-propagate the information around from meta data stored with the roots. This
-often eliminates the need to have a header on objects in the heap. This is
-common in the ML family.</li>
-
-<li>If all heap objects have pointers in the same locations, or pointers can be
-distinguished just by looking at them (e.g., the low order bit is clear), no
-book-keeping is needed at all. This is common for Lisp-like languages.</li>
-</ol>
-
-<p>The LLVM garbage collectors are capable of supporting all of these styles of
-language, including ones that mix various implementations. To do this, it
-allows the source-language to associate meta-data with the <a
-href="#gcroot">stack roots</a>, and the heap tracing routines can propagate the
-information. In addition, LLVM allows the front-end to extract GC information
-in any form from a specific object pointer (this supports situations #1 and #3).
-</p>
-
-</div>
-