diff --git a/llvm/include/llvm/Analysis/LoopInfo.h b/llvm/include/llvm/Analysis/LoopInfo.h
index 7c89744123fd..12cb6c5cc480 100644
--- a/llvm/include/llvm/Analysis/LoopInfo.h
+++ b/llvm/include/llvm/Analysis/LoopInfo.h
@@ -33,6 +33,7 @@
 
 #include "llvm/Pass.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/GraphTraits.h"
 #include "llvm/ADT/SmallVector.h"
@@ -484,12 +485,13 @@ public:
   }
 
   /// verifyLoop - Verify loop structure of this loop and all nested loops.
-  void verifyLoopNest() const {
+  void verifyLoopNest(DenseSet<const LoopT*> *Loops) const {
+    Loops->insert(static_cast<const LoopT *>(this));
     // Verify this loop.
     verifyLoop();
     // Verify the subloops.
     for (iterator I = begin(), E = end(); I != E; ++I)
-      (*I)->verifyLoopNest();
+      (*I)->verifyLoopNest(Loops);
   }
 
   void print(raw_ostream &OS, unsigned Depth = 0) const {
@@ -640,6 +642,7 @@ class LoopInfoBase {
   DenseMap<BlockT *, LoopT *> BBMap;
   std::vector<LoopT *> TopLevelLoops;
   friend class LoopBase<BlockT, LoopT>;
+  friend class LoopInfo;
 
   void operator=(const LoopInfoBase &); // do not implement
   LoopInfoBase(const LoopInfo &);       // do not implement
diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index 6abb14f55ae5..85aaccaefc37 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -509,6 +509,8 @@ void UnloopUpdater::updateSubloopParents() {
     assert(SubloopParents.count(Subloop) && "DFS failed to visit subloop");
     if (SubloopParents[Subloop])
       SubloopParents[Subloop]->addChildLoop(Subloop);
+    else
+      LI->addTopLevelLoop(Subloop);
   }
 }
 
@@ -663,12 +665,21 @@ void LoopInfo::verifyAnalysis() const {
 
   if (!VerifyLoopInfo) return;
 
+  DenseSet<const Loop*> Loops;
   for (iterator I = begin(), E = end(); I != E; ++I) {
     assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
-    (*I)->verifyLoopNest();
+    (*I)->verifyLoopNest(&Loops);
   }
 
-  // TODO: check BBMap consistency.
+  // Verify that blocks are mapped to valid loops.
+  //
+  // FIXME: With an up-to-date DFS (see LoopIterator.h) and DominatorTree, we
+  // could also verify that the blocks are still in the correct loops.
+  for (DenseMap<BasicBlock*, Loop*>::const_iterator I = LI.BBMap.begin(),
+         E = LI.BBMap.end(); I != E; ++I) {
+    assert(Loops.count(I->second) && "orphaned loop");
+    assert(I->second->contains(I->first) && "orphaned block");
+  }
 }
 
 void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {