diff --git a/llvm/include/llvm/Analysis/LoopInfo.h b/llvm/include/llvm/Analysis/LoopInfo.h
--- a/llvm/include/llvm/Analysis/LoopInfo.h
+++ b/llvm/include/llvm/Analysis/LoopInfo.h
@@ -201,9 +201,10 @@
   }
 
   /// True if terminator in the block can branch to another block that is
-  /// outside of the current loop.
+  /// outside of the current loop. \p BB must be inside the loop.
   bool isLoopExiting(const BlockT *BB) const {
     assert(!isInvalid() && "Loop not in a valid state!");
+    assert(contains(BB) && "Exiting block must be part of the loop");
     for (const auto &Succ : children<const BlockT *>(BB)) {
       if (!contains(Succ))
         return true;
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp b/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetTransformInfo.cpp
@@ -117,8 +117,10 @@
       // Add a small bonus for each of such "if" statements.
       if (const BranchInst *Br = dyn_cast<BranchInst>(&I)) {
         if (UP.Threshold < MaxBoost && Br->isConditional()) {
-          if (L->isLoopExiting(Br->getSuccessor(0)) ||
-              L->isLoopExiting(Br->getSuccessor(1)))
+          BasicBlock *Succ0 = Br->getSuccessor(0);
+          BasicBlock *Succ1 = Br->getSuccessor(1);
+          if ((L->contains(Succ0) && L->isLoopExiting(Succ0)) ||
+              (L->contains(Succ1) && L->isLoopExiting(Succ1)))
             continue;
           if (dependsOnLocalPhi(L, Br->getCondition())) {
             UP.Threshold += UnrollThresholdIf;