Index: llvm/lib/Transforms/Utils/CloneFunction.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -739,12 +739,12 @@
                                    const Twine &NameSuffix, LoopInfo *LI,
                                    DominatorTree *DT,
                                    SmallVectorImpl<BasicBlock *> &Blocks) {
-  assert(OrigLoop->getSubLoops().empty() &&
-         "Loop to be cloned cannot have inner loop");
   Function *F = OrigLoop->getHeader()->getParent();
   Loop *ParentLoop = OrigLoop->getParentLoop();
+  std::map<Loop *, Loop *> LMap;
 
   Loop *NewLoop = LI->AllocateLoop();
+  LMap[OrigLoop] = NewLoop;
   if (ParentLoop)
     ParentLoop->addChildLoop(NewLoop);
   else
@@ -765,11 +765,28 @@
   DT->addNewBlock(NewPH, LoopDomBB);
 
   for (BasicBlock *BB : OrigLoop->getBlocks()) {
+    Loop *CurLoop = LI->getLoopFor(BB);
+    Loop *NewLoop = LMap[CurLoop];
+    if (!NewLoop) {
+      NewLoop = LI->AllocateLoop();
+      LMap[CurLoop] = NewLoop;
+
+      // Establish the parent/child relationship.
+      Loop *OrigParent = CurLoop->getParentLoop();
+      assert(OrigParent && "Could not find the original parent loop");
+      Loop *NewParentLoop = LMap[OrigParent];
+      assert(NewParentLoop && "Could not find the new parent loop");
+
+      NewParentLoop->addChildLoop(NewLoop);
+    }
+
     BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix, F);
     VMap[BB] = NewBB;
 
     // Update LoopInfo.
     NewLoop->addBasicBlockToLoop(NewBB, *LI);
+    if (BB == CurLoop->getHeader())
+      NewLoop->moveToHeader(NewBB);
 
     // Add DominatorTree node. After seeing all blocks, update to correct IDom.
     DT->addNewBlock(NewBB, NewPH);