AMDGPU: Error in SIAnnotateControlFlow instead of assert

[arsenm]

Summary

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.

[cfang]

lib/Target/AMDGPU/SIAnnotateControlFlow.cpp

428

Does the annotation pass have the requirement of structurized CFG? I remember that there is an OpenMP
code with a conditional branch to a block with a unreachable instruction. Is that CFG unstructurized?

[arsenm]

lib/Target/AMDGPU/SIAnnotateControlFlow.cpp

428

Yes, the structurizer is a separate pass

[cfang]

LGTM

[arsenm]

r322685

lib/Target/AMDGPU/SIAnnotateControlFlow.cpp

if (isTopOfStack(BB)) {
       }
 
       closeControlFlow(BB);
     }
 
     openIf(Term);
   }
 
-  assert(Stack.empty());
+  if (!Stack.empty()) {
+    // CFG was probably not structured.
+    report_fatal_error("failed to annotate CFG");
+  }
+
   return true;
 }
 
 /// \brief Create the annotation pass
 FunctionPass *llvm::createSIAnnotateControlFlowPass() {
   return new SIAnnotateControlFlow();
 }