Index: llvm/lib/Transforms/Utils/LoopUnroll.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUnroll.cpp
+++ llvm/lib/Transforms/Utils/LoopUnroll.cpp
@@ -763,13 +763,6 @@
     }
   }
 
-  // When completely unrolling, the last latch becomes unreachable.
-  if (!LatchIsExiting && CompletelyUnroll) {
-    BranchInst *Term = cast<BranchInst>(Latches.back()->getTerminator());
-    new UnreachableInst(Term->getContext(), Term);
-    Term->eraseFromParent();
-  }
-
   // Update dominators of blocks we might reach through exits.
   // Immediate dominator of such block might change, because we add more
   // routes which can lead to the exit: we can now reach it from the copied
@@ -819,6 +812,12 @@
          DT->verify(DominatorTree::VerificationLevel::Fast));
 
   DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Lazy);
+
+  // When completely unrolling, the last latch becomes unreachable.
+  if (!LatchIsExiting && CompletelyUnroll)
+    changeToUnreachable(&Latches.back()->front(), /* UseTrap */ false,
+                        PreserveLCSSA, &DTU);
+
   // Merge adjacent basic blocks, if possible.
   for (BasicBlock *Latch : Latches) {
     BranchInst *Term = dyn_cast<BranchInst>(Latch->getTerminator());
Index: llvm/test/Transforms/LoopUnroll/unroll-unconditional-latch.ll
===================================================================
--- llvm/test/Transforms/LoopUnroll/unroll-unconditional-latch.ll
+++ llvm/test/Transforms/LoopUnroll/unroll-unconditional-latch.ll
@@ -28,7 +28,6 @@
 ; CHECK-NEXT:    store i32 0, i32* [[PTR_3]], align 4
 ; CHECK-NEXT:    br i1 true, label [[IF_END_LOOPEXIT:%.*]], label [[FOR_LATCH_3:%.*]]
 ; CHECK:       for.latch.3:
-; CHECK-NEXT:    store volatile i64 3, i64* [[OUT]], align 4
 ; CHECK-NEXT:    unreachable
 ;