This ensures that the last child indexes are calculated in linear time andDo the single hash calculation before acquiring the lock, to reduce
can later be queried in constant time by getLastChild.
The baseline situation was that individual calls to getLastChild were linear in thelock contention. If Copy is true, and the string was not yet contained
size of DieArray.in the StringStorage, Calling getLastChild once for every DWARFDebugInfoEntry was
amortized quadratic in the size of DieArray.use the new address from StringStorage, but
reuse the hash we already calculated.