[Attributor][NFC] Invalid DerefState is at fixpoint

Summary:
If the DerefBytesState (and thereby the DerefState) is invalid, we
reached a fixpoint for the whole DerefState as we will not
manifest/provide information then.

Reviewers: uenoku, sstefan1

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65586

llvm-svn: 367789

llvm/lib/Transforms/IPO/Attributor.cpp

@@ -1757,9 +1757,10 @@ struct DerefState : AbstractState {
   /// See AbstractState::isValidState()
   bool isValidState() const override { return DerefBytesState.isValidState(); }
 
-  // See AbstractState::isAtFixpoint()
+  /// See AbstractState::isAtFixpoint()
   bool isAtFixpoint() const override {
-    return DerefBytesState.isAtFixpoint() && NonNullGlobalState.isAtFixpoint();
+    return !isValidState() || (DerefBytesState.isAtFixpoint() &&
+                               NonNullGlobalState.isAtFixpoint());
   }
 
   /// See AbstractState::indicateOptimisticFixpoint(...)