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
@@ -112,6 +112,8 @@
   bool MaybeMergeBasicBlockIntoOnlyPred(BasicBlock *BB);
   void UpdateSSA(BasicBlock *BB, BasicBlock *NewBB,
                  DenseMap<Instruction *, Value *> &ValueMapping);
+  std::pair<BasicBlock *, DenseMap<Instruction *, Value *>>
+      CloneBasicBlock(BasicBlock *BB, BasicBlock* PredBB);
   bool ThreadEdge(BasicBlock *BB, const SmallVectorImpl<BasicBlock *> &PredBBs,
                   BasicBlock *SuccBB);
   bool DuplicateCondBranchOnPHIIntoPred(
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
@@ -1973,6 +1973,58 @@
   }
 }
 
+/// Clone basic block BB except its terminator just for predecessor PredBB.
+/// Return the newly created basic block and the map from the variables in BB to
+/// the variables in the newly created basic block.
+std::pair<BasicBlock *, DenseMap<Instruction *, Value *>>
+JumpThreadingPass::CloneBasicBlock(BasicBlock *BB, BasicBlock* PredBB) {
+  // We are going to have to map operands from the original BB block to the new
+  // copy of the block 'NewBB'.  If there are PHI nodes in BB, evaluate them to
+  // account for entry from PredBB.
+  DenseMap<Instruction*, Value*> ValueMapping;
+
+  BasicBlock *NewBB = BasicBlock::Create(BB->getContext(),
+                                         BB->getName()+".thread",
+                                         BB->getParent(), BB);
+  NewBB->moveAfter(PredBB);
+
+  // Set the block frequency of NewBB.
+  if (HasProfileData) {
+    auto NewBBFreq =
+        BFI->getBlockFreq(PredBB) * BPI->getEdgeProbability(PredBB, BB);
+    BFI->setBlockFreq(NewBB, NewBBFreq.getFrequency());
+  }
+
+  BasicBlock::iterator BI = BB->begin();
+  // Clone the phi nodes of BB into NewBB. The resulting phi nodes are trivial,
+  // since NewBB only has one predecessor, but SSAUpdater might need to rewrite
+  // the operand of the cloned phi.
+  for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI) {
+    PHINode *NewPN = PHINode::Create(PN->getType(), 1, PN->getName(), NewBB);
+    NewPN->addIncoming(PN->getIncomingValueForBlock(PredBB), PredBB);
+    ValueMapping[PN] = NewPN;
+  }
+
+  // Clone the non-phi instructions of BB into NewBB, keeping track of the
+  // mapping and using it to remap operands in the cloned instructions.
+  for (; !BI->isTerminator(); ++BI) {
+    Instruction *New = BI->clone();
+    New->setName(BI->getName());
+    NewBB->getInstList().push_back(New);
+    ValueMapping[&*BI] = New;
+
+    // Remap operands to patch up intra-block references.
+    for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
+      if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
+        DenseMap<Instruction*, Value*>::iterator I = ValueMapping.find(Inst);
+        if (I != ValueMapping.end())
+          New->setOperand(i, I->second);
+      }
+  }
+
+  return {NewBB, ValueMapping};
+}
+
 /// 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.
@@ -2030,49 +2082,9 @@
     LVI->enableDT();
   LVI->threadEdge(PredBB, BB, SuccBB);
 
-  // We are going to have to map operands from the original BB block to the new
-  // copy of the block 'NewBB'.  If there are PHI nodes in BB, evaluate them to
-  // account for entry from PredBB.
   DenseMap<Instruction*, Value*> ValueMapping;
-
-  BasicBlock *NewBB = BasicBlock::Create(BB->getContext(),
-                                         BB->getName()+".thread",
-                                         BB->getParent(), BB);
-  NewBB->moveAfter(PredBB);
-
-  // Set the block frequency of NewBB.
-  if (HasProfileData) {
-    auto NewBBFreq =
-        BFI->getBlockFreq(PredBB) * BPI->getEdgeProbability(PredBB, BB);
-    BFI->setBlockFreq(NewBB, NewBBFreq.getFrequency());
-  }
-
-  BasicBlock::iterator BI = BB->begin();
-  // Clone the phi nodes of BB into NewBB. The resulting phi nodes are trivial,
-  // since NewBB only has one predecessor, but SSAUpdater might need to rewrite
-  // the operand of the cloned phi.
-  for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI) {
-    PHINode *NewPN = PHINode::Create(PN->getType(), 1, PN->getName(), NewBB);
-    NewPN->addIncoming(PN->getIncomingValueForBlock(PredBB), PredBB);
-    ValueMapping[PN] = NewPN;
-  }
-
-  // Clone the non-phi instructions of BB into NewBB, keeping track of the
-  // mapping and using it to remap operands in the cloned instructions.
-  for (; !BI->isTerminator(); ++BI) {
-    Instruction *New = BI->clone();
-    New->setName(BI->getName());
-    NewBB->getInstList().push_back(New);
-    ValueMapping[&*BI] = New;
-
-    // Remap operands to patch up intra-block references.
-    for (unsigned i = 0, e = New->getNumOperands(); i != e; ++i)
-      if (Instruction *Inst = dyn_cast<Instruction>(New->getOperand(i))) {
-        DenseMap<Instruction*, Value*>::iterator I = ValueMapping.find(Inst);
-        if (I != ValueMapping.end())
-          New->setOperand(i, I->second);
-      }
-  }
+  BasicBlock *NewBB;
+  std::tie(NewBB, ValueMapping) = CloneBasicBlock(BB, PredBB);
 
   // We didn't copy the terminator from BB over to NewBB, because there is now
   // an unconditional jump to SuccBB.  Insert the unconditional jump.