diff --git a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
--- a/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
+++ b/llvm/include/llvm/Transforms/Scalar/JumpThreading.h
@@ -116,7 +116,7 @@
                                                      BasicBlock::iterator BE,
                                                      BasicBlock *NewBB,
                                                      BasicBlock *PredBB);
-  bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
+  void ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
                   BasicBlock *SuccBB);
   bool DuplicateCondBranchOnPHIIntoPred(
       BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs);
diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -1717,8 +1717,40 @@
     MostPopularDest = BB->getTerminator()->
                             getSuccessor(GetBestDestForJumpOnUndef(BB));
 
+  // If threading to the same block as we come from, we would infinite loop.
+  if (MostPopularDest == BB) {
+    LLVM_DEBUG(dbgs() << "  Not threading across BB '" << BB->getName()
+                      << "' - would thread to self!\n");
+    return false;
+  }
+
+  // If threading this would thread across a loop header, don't thread the edge.
+  // See the comments above FindLoopHeaders for justifications and caveats.
+  if (LoopHeaders.count(BB) || LoopHeaders.count(MostPopularDest)) {
+    LLVM_DEBUG({
+      bool BBIsHeader = LoopHeaders.count(BB);
+      bool SuccIsHeader = LoopHeaders.count(MostPopularDest);
+      dbgs() << "  Not threading across "
+             << (BBIsHeader ? "loop header BB '" : "block BB '")
+             << BB->getName() << "' to dest "
+             << (SuccIsHeader ? "loop header BB '" : "block BB '")
+             << MostPopularDest->getName()
+             << "' - it might create an irreducible loop!\n";
+    });
+    return false;
+  }
+
+  unsigned JumpThreadCost =
+      getJumpThreadDuplicationCost(BB, BB->getTerminator(), BBDupThreshold);
+  if (JumpThreadCost > BBDupThreshold) {
+    LLVM_DEBUG(dbgs() << "  Not threading BB '" << BB->getName()
+                      << "' - Cost is too high: " << JumpThreadCost << "\n");
+    return false;
+  }
+
   // Ok, try to thread it!
-  return ThreadEdge(BB, PredsToFactor, MostPopularDest);
+  ThreadEdge(BB, PredsToFactor, MostPopularDest);
+  return true;
 }
 
 /// ProcessBranchOnPHI - We have an otherwise unthreadable conditional branch on
@@ -2019,38 +2051,9 @@
 /// ThreadEdge - We have decided that it is safe and profitable to factor the
 /// blocks in PredBBs to one predecessor, then thread an edge from it to SuccBB
 /// across BB.  Transform the IR to reflect this change.
-bool JumpThreadingPass::ThreadEdge(BasicBlock *BB,
+void JumpThreadingPass::ThreadEdge(BasicBlock *BB,
                                    const SmallVectorImpl<BasicBlock *> &PredBBs,
                                    BasicBlock *SuccBB) {
-  // If threading to the same block as we come from, we would infinite loop.
-  if (SuccBB == BB) {
-    LLVM_DEBUG(dbgs() << "  Not threading across BB '" << BB->getName()
-                      << "' - would thread to self!\n");
-    return false;
-  }
-
-  // If threading this would thread across a loop header, don't thread the edge.
-  // See the comments above FindLoopHeaders for justifications and caveats.
-  if (LoopHeaders.count(BB) || LoopHeaders.count(SuccBB)) {
-    LLVM_DEBUG({
-      bool BBIsHeader = LoopHeaders.count(BB);
-      bool SuccIsHeader = LoopHeaders.count(SuccBB);
-      dbgs() << "  Not threading across "
-          << (BBIsHeader ? "loop header BB '" : "block BB '") << BB->getName()
-          << "' to dest " << (SuccIsHeader ? "loop header BB '" : "block BB '")
-          << SuccBB->getName() << "' - it might create an irreducible loop!\n";
-    });
-    return false;
-  }
-
-  unsigned JumpThreadCost =
-      getJumpThreadDuplicationCost(BB, BB->getTerminator(), BBDupThreshold);
-  if (JumpThreadCost > BBDupThreshold) {
-    LLVM_DEBUG(dbgs() << "  Not threading BB '" << BB->getName()
-                      << "' - Cost is too high: " << JumpThreadCost << "\n");
-    return false;
-  }
-
   // And finally, do it!  Start by factoring the predecessors if needed.
   BasicBlock *PredBB;
   if (PredBBs.size() == 1)
@@ -2064,7 +2067,6 @@
   // And finally, do it!
   LLVM_DEBUG(dbgs() << "  Threading edge from '" << PredBB->getName()
                     << "' to '" << SuccBB->getName()
-                    << "' with cost: " << JumpThreadCost
                     << ", across block:\n    " << *BB << "\n");
 
   if (DTU->hasPendingDomTreeUpdates())
@@ -2125,7 +2127,6 @@
 
   // Threaded an edge!
   ++NumThreads;
-  return true;
 }
 
 /// Create a new basic block that will be the predecessor of BB and successor of