Predicate TrackedVariablesImpl::trackField

Holds if f is a field that is interesting as a basis for SSA.

• A field that is read twice is interesting as we want to know whether the reads refer to the same value.
• A field that is both written and read is interesting as we want to know whether the read might get the written value.
• A field that is read in a loop is interesting as we want to know whether the value is the same in different iterations (that is, whether the SSA definition can be placed outside the loop).
• A volatile field is never interesting, since all reads must reread from memory and we are forced to assume that the value can change at any point.