Index: lib/Transforms/Scalar/LoopUnswitch.cpp
===================================================================
--- lib/Transforms/Scalar/LoopUnswitch.cpp
+++ lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -593,13 +593,47 @@
       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 *BInst = dyn_cast<BranchInst>(DomBB->getTerminator());
+
+        Node = DT->getNode(DomBB)->getIDom();
+        DomBB = Node->getBlock();
+
+        if (!BInst || !BInst->isConditional())
+          continue;
+
+        Value *Cond = BInst->getCondition();
+        if (!isa<ConstantInt>(Cond))
+          continue;
+
+        BasicBlock *UnreachableSucc =
+            Cond == ConstantInt::getTrue(Cond->getContext())
+                ? BInst->getSuccessor(1)
+                : BInst->getSuccessor(0);
+
+        BasicBlockEdge UnreachableEdge(BInst->getParent(), UnreachableSucc);
+        if (DT->dominates(UnreachableEdge, *I)) {
+          isUnreachable = true;
+          break;
+        }
+      }
+
+      if (isUnreachable)
+        continue;
+
       // If this isn't branching on an invariant condition, we can't unswitch
       // it.
       if (BI->isConditional()) {
         // See if this, or some part of it, is loop invariant.  If so, we can
         // unswitch on it if we desire.
-        Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
-                                               currentLoop, Changed);
+        Value *LoopCond =
+            FindLIVLoopCondition(BI->getCondition(), currentLoop, Changed);
         if (LoopCond &&
             UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context), TI)) {
           ++NumBranches;
Index: test/Transforms/LoopUnswitch/elseif-non-exponential-behavior.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnswitch/elseif-non-exponential-behavior.ll
@@ -0,0 +1,68 @@
+; REQUIRES: asserts
+; RUN: opt < %s -O3 -loop-unswitch -stats -disable-output 2>&1 | grep "2 loop-unswitch    - Number of branches unswitched" | count 1
+
+; Function Attrs: nounwind uwtable
+define i32 @b(i32 %x, i32 %y) #0 {
+entry:
+  %x.addr = alloca i32, align 4
+  %y.addr = alloca i32, align 4
+  %pdt = alloca i32, align 4
+  %i = alloca i32, align 4
+  store i32 %x, i32* %x.addr, align 4
+  store i32 %y, i32* %y.addr, align 4
+  store i32 1, i32* %pdt, align 4
+  store i32 0, i32* %i, align 4
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc, %entry
+  %0 = load i32, i32* %i, align 4
+  %cmp = icmp slt i32 %0, 100
+  br i1 %cmp, label %for.body, label %for.end
+
+for.body:                                         ; preds = %for.cond
+  %1 = load i32, i32* %x.addr, align 4
+  %tobool = icmp ne i32 %1, 0
+  br i1 %tobool, label %if.then, label %if.else
+
+if.then:                                          ; preds = %for.body
+  %2 = load i32, i32* %pdt, align 4
+  %mul = mul nsw i32 %2, 2
+  store i32 %mul, i32* %pdt, align 4
+  br label %if.end6
+
+if.else:                                          ; preds = %for.body
+  %3 = load i32, i32* %y.addr, align 4
+  %tobool1 = icmp ne i32 %3, 0
+  br i1 %tobool1, label %if.then2, label %if.else4
+
+if.then2:                                         ; preds = %if.else
+  %4 = load i32, i32* %pdt, align 4
+  %mul3 = mul nsw i32 %4, 3
+  store i32 %mul3, i32* %pdt, align 4
+  br label %if.end
+
+if.else4:                                         ; preds = %if.else
+  %5 = load i32, i32* %pdt, align 4
+  %mul5 = mul nsw i32 %5, 4
+  store i32 %mul5, i32* %pdt, align 4
+  br label %if.end
+
+if.end:                                           ; preds = %if.else4, %if.then2
+  br label %if.end6
+
+if.end6:                                          ; preds = %if.end, %if.then
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.end6
+  %6 = load i32, i32* %i, align 4
+  %inc = add nsw i32 %6, 1
+  store i32 %inc, i32* %i, align 4
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  %7 = load i32, i32* %pdt, align 4
+  ret i32 %7
+}
+
+
+