These two fields are reported as only written to, but not read from anywhere:

class CallStaticJavaNode : public CallJavaNode {
  ...
  // Result of Escape Analysis
  bool _is_scalar_replaceable;
  bool _is_non_escaping;
}

There are accesses to AllocNode::{_is_scalar_replaceable,_is_non_escaping}, but not to CallStaticJavaNode.
This is either a bug, or more likely a leftover from EliminateAutoBox work, as these fields were introduced by JDK-6934604.