Add a comment for a todo in LoopUnroll post cleanup

llvm-svn: 290769

llvm/lib/Transforms/Utils/LoopUnroll.cpp

@@ -673,6 +673,11 @@ bool llvm::UnrollLoop(Loop *L, unsigned Count, unsigned TripCount, bool Force,
     }
   }
 
+  // TODO: after peeling or unrolling, previously loop variant conditions are
+  // likely to fold to constants, eagerly propagating those here will require
+  // fewer cleanup passes to be run.  Alternatively, a LoopEarlyCSE might be
+  // appropriate.
+
   NumCompletelyUnrolled += CompletelyUnroll;
   ++NumUnrolled;