Make a note that this is usually used via bugpoint.

llvm-svn: 12068
diff --git a/llvm/lib/Transforms/Utils/LoopExtractor.cpp b/llvm/lib/Transforms/Utils/LoopExtractor.cpp
index da97b5f..3eda452 100644
--- a/llvm/lib/Transforms/Utils/LoopExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/LoopExtractor.cpp
@@ -2,7 +2,8 @@
 //
 // A pass wrapper around the ExtractLoop() scalar transformation to extract each
 // top-level loop into its own new function. If the loop is the ONLY loop in a
-// given function, it is not touched.
+// given function, it is not touched. This is a pass most useful for debugging
+// via bugpoint.
 //
 //===----------------------------------------------------------------------===//
 
@@ -58,8 +59,6 @@
   return Changed;
 }
 
-
-
 } // End anonymous namespace 
 
 /// createLoopExtractorPass