diff --git a/llvm/docs/TestingGuide.html b/llvm/docs/TestingGuide.html
index 60fe18a8e5a6..7c2b42d25bbb 100644
--- a/llvm/docs/TestingGuide.html
+++ b/llvm/docs/TestingGuide.html
@@ -29,6 +29,7 @@
   <li><a href="#dgstructure">DejaGNU structure</a>
     <ul>
       <li><a href="#dgcustom">Writing new DejaGNU tests</a></li>
+      <li><a href="#FileCheck">The FileCheck utility</a></li>
       <li><a href="#dgvars">Variables and substitutions</a></li>
       <li><a href="#dgfeatures">Other features</a></li>
    </ul>
@@ -447,6 +448,26 @@ negatives).</p>
 
 </div>
 
+<!-- _______________________________________________________________________ -->
+<div class="doc_subsection"><a name="FileCheck">The FileCheck utility</a></div>
+<!-- _______________________________________________________________________ -->
+
+<div class="doc_text">
+
+<p>A powerful feature of the RUN: lines is that it allows any arbitrary commands
+   to be executed as part of the test harness.  While standard (portable) unix
+   tools like 'grep' work fine on run lines, as you see above, there are a lot
+   of caveats due to interaction with Tcl syntax, and we want to make that the
+   run lines are portable to a wide range of systems.  Another major problem is
+   that grep is not very good at checking to verify that the output of a tools
+   contains a series of different output in a specific order.  The FileCheck
+   tool was designed to help with these problems.</p>
+
+
+<!-- http://llvm.org/cmds/FileCheck.html -->
+
+</div>
+
 <!-- _______________________________________________________________________ -->
 <div class="doc_subsection"><a name="dgvars">Variables and substitutions</a></div>
 <!-- _______________________________________________________________________ -->