This ticket is raised to migrate (as per Maurizio's suggestion ) a bunch of
assertions that were introduced in Javac's code generator for valhalla
under this change set:
http://hg.openjdk.java.net/valhalla/valhalla/langtools/rev/2a7cae3ea93d

These assertions also hold true for JDK9 dev and can contribute to
code clarity and maintainability.