CSE cache release tracking #100
Description
For common subexpression elimination we maintain a cache of partial results in the CSECacheTable. This table is built when we first scan an expression for common subexpressions, and we note the count of how frequently that subexpression occurs. If that count is more than one, then we store the result of a subexpression for future re-use.
However, the partial results will be held into the table until the end of the evaluation of the entire expression, meaning we hold onto more active memory than we need to.
The CSECacheTable has in it how many times the data is used, so we could count how frequently it is read and deallocate that cache entry once it has been read the expected number of times.