diff --git a/llvm/lib/Transforms/Utils/LoopSimplify.cpp b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
--- a/llvm/lib/Transforms/Utils/LoopSimplify.cpp
+++ b/llvm/lib/Transforms/Utils/LoopSimplify.cpp
@@ -728,15 +728,8 @@
 
   // Worklist maintains our depth-first queue of loops in this nest to process.
   SmallVector<Loop *, 4> Worklist;
-  Worklist.push_back(L);
-
-  // Walk the worklist from front to back, pushing newly found sub loops onto
-  // the back. This will let us process loops from back to front in depth-first
-  // order. We can use this simple process because loops form a tree.
-  for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
-    Loop *L2 = Worklist[Idx];
-    Worklist.append(L2->begin(), L2->end());
-  }
+  for_each(depth_first(L),
+           [&Worklist](Loop *SubLoop) { Worklist.push_back(SubLoop); });
 
   while (!Worklist.empty())
     Changed |= simplifyOneLoop(Worklist.pop_back_val(), Worklist, DT, LI, SE,