Index: lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
===================================================================
--- lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
+++ lib/Target/AMDGPU/SIAnnotateControlFlow.cpp
@@ -422,7 +422,11 @@
     openIf(Term);
   }
 
-  assert(Stack.empty());
+  if (!Stack.empty()) {
+    // CFG was probably not structured.
+    report_fatal_error("failed to annotate CFG");
+  }
+
   return true;
 }