Make a note that this is usually used via bugpoint.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12068 91177308-0d34-0410-b5e6-96231b3b80d8

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 @@ bool LoopExtractor::runOnFunction(Function &F) {
   return Changed;
 }
 
-
-
 } // End anonymous namespace 
 
 /// createLoopExtractorPass