Index: lib/Transforms/Utils/LoopUnrollRuntime.cpp
===================================================================
--- lib/Transforms/Utils/LoopUnrollRuntime.cpp
+++ lib/Transforms/Utils/LoopUnrollRuntime.cpp
@@ -545,13 +545,27 @@
   BasicBlock *Header = L->getHeader();
 
   BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
+
+  if (!LatchBR || LatchBR->isUnconditional()) {
+    // The loop-rotate pass can be helpful to avoid this in many cases.
+    LLVM_DEBUG(
+        dbgs()
+        << "Loop latch not terminated by a conditional branch.\n");
+    return false;
+  }
+
   unsigned ExitIndex = LatchBR->getSuccessor(0) == Header ? 1 : 0;
   BasicBlock *LatchExit = LatchBR->getSuccessor(ExitIndex);
-  // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
-  // targets of the Latch be an exit block out of the loop. This needs
-  // to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
-  assert(!L->contains(LatchExit) &&
-         "one of the loop latch successors should be the exit block!");
+
+  if (L->contains(LatchExit)) {
+    // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one of the
+    // targets of the Latch be an exit block out of the loop.
+    LLVM_DEBUG(
+        dbgs()
+        << "One of the loop latch successors must be the exit block.\n");
+    return false;
+  }
+
   // These are exit blocks other than the target of the latch exiting block.
   SmallVector<BasicBlock *, 4> OtherExits;
   bool isMultiExitUnrollingEnabled =
Index: test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll
===================================================================
--- test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll
+++ test/Transforms/LoopUnroll/runtime-loop-non-exiting-latch.ll
@@ -0,0 +1,27 @@
+; RUN: opt < %s -S -loop-unroll -unroll-runtime=true -unroll-allow-remainder=true -unroll-count=4
+
+; Make sure that the runtime unroll does not break with a non-exiting latch.
+
+define i32 @test(i32* %a, i32* %b, i32* %c, i64 %n) {
+entry:
+  br label %while.cond
+
+while.cond:                                       ; preds = %while.body, %entry
+  %i.0 = phi i64 [ 0, %entry ], [ %inc, %while.body ]
+  %cmp = icmp slt i64 %i.0, %n
+  br i1 %cmp, label %while.body, label %while.end
+
+while.body:                                       ; preds = %while.cond
+  %arrayidx = getelementptr inbounds i32, i32* %b, i64 %i.0
+  %0 = load i32, i32* %arrayidx
+  %arrayidx1 = getelementptr inbounds i32, i32* %c, i64 %i.0
+  %1 = load i32, i32* %arrayidx1
+  %mul = mul nsw i32 %0, %1
+  %arrayidx2 = getelementptr inbounds i32, i32* %a, i64 %i.0
+  store i32 %mul, i32* %arrayidx2
+  %inc = add nsw i64 %i.0, 1
+  br label %while.cond
+
+while.end:                                        ; preds = %while.cond
+  ret i32 0
+}