AMDGPU: Error in SIAnnotateControlFlow instead of assert

This assert typically happens if an unstructured CFG is passed
to the pass. This can happen if the pass is run independently
without the structurizer.

llvm-svn: 322685

lib/Target/AMDGPU/SIAnnotateControlFlow.cpp

@@ -422,7 +422,11 @@ bool SIAnnotateControlFlow::runOnFunction(Function &F) {
     openIf(Term);
   }
 
-  assert(Stack.empty());
+  if (!Stack.empty()) {
+    // CFG was probably not structured.
+    report_fatal_error("failed to annotate CFG");
+  }
+
   return true;
 }