This forward declaration has been deprecated.
I guess it's a leftover after refactoring.
https://github.com/openjdk/jdk/search?q=PhaseCCP_DCE&unscoped_q=PhaseCCP_DCE
I guess it's a leftover after refactoring.
https://github.com/openjdk/jdk/search?q=PhaseCCP_DCE&unscoped_q=PhaseCCP_DCE