Index: lib/Transforms/Scalar/LoopUnswitch.cpp
===================================================================
--- lib/Transforms/Scalar/LoopUnswitch.cpp
+++ lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -593,6 +593,45 @@
       continue;
 
     if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+     /*
+      * Some branches may be rendered unreachable because of previous unswitching.
+      * Unswitch only those branches that are reachable.
+      */
+      auto *Node = DT->getNode(*I)->getIDom();
+      BasicBlock *DomBB = Node->getBlock();
+      bool isUnreachable = false;
+      while (currentLoop->contains(DomBB)) {
+          BranchInst *BI = dyn_cast<BranchInst> (DomBB->getTerminator());
+
+          if (BI && BI->isConditional()) {
+             Value *Cond = BI->getCondition();
+             BasicBlock *Succ = NULL;
+             if (Cond == ConstantInt::getTrue(Cond->getContext())) {
+                Succ = BI->getSuccessor(1);
+             } else if (Cond == ConstantInt::getFalse(Cond->getContext())){
+                Succ = BI->getSuccessor(0);
+             }
+
+             if (Succ) {
+                BasicBlockEdge UnreachableEdge (BI->getParent(), Succ);
+                if (DT->dominates(UnreachableEdge, *I)) {
+                   isUnreachable = true;
+                   break;
+                }
+             }
+          }
+
+          if (isUnreachable) break;
+
+          Node = DT->getNode(DomBB)->getIDom();
+          DomBB = Node->getBlock();
+      }
+
+      if (isUnreachable) {
+        DEBUG (dbgs() << "Unreachable branch: " << *TI << " in Function " << (*I)->getParent()->getName() << "\n");
+        continue;
+      }
+
       // If this isn't branching on an invariant condition, we can't unswitch
       // it.
       if (BI->isConditional()) {