Index: llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
+++ llvm/trunk/lib/Transforms/Utils/LoopUnroll.cpp
@@ -54,10 +54,10 @@
 static cl::opt<bool>
 UnrollVerifyDomtree("unroll-verify-domtree", cl::Hidden,
                     cl::desc("Verify domtree after unrolling"),
-#ifdef NDEBUG
-    cl::init(false)
-#else
+#ifdef EXPENSIVE_CHECKS
     cl::init(true)
+#else
+    cl::init(false)
 #endif
                     );
 
Index: llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -615,7 +615,9 @@
       // the original loop body.
       if (Iter == 0)
         DT->changeImmediateDominator(Exit, cast<BasicBlock>(LVMap[Latch]));
+#ifdef EXPENSIVE_CHECKS
       assert(DT->verify(DominatorTree::VerificationLevel::Fast));
+#endif
     }
 
     auto *LatchBRCopy = cast<BranchInst>(VMap[LatchBR]);