/// RehashTable - Grow the table, redistributing values into the buckets with
/// the appropriate mod-of-hashtable-size.
void StringMapImpl::RehashTable() {
- unsigned NewSize = NumBuckets*2;
+ unsigned NewSize;
+
+ // If the hash table is now more than 3/4 full, or if fewer than 1/8 of
+ // the buckets are empty (meaning that many are filled with tombstones),
+ // grow/rehash the table.
+ if (NumItems*4 > NumBuckets*3) {
+ NewSize = NumBuckets*2;
+ } else if (NumBuckets-(NumItems+NumTombstones) < NumBuckets/8) {
+ NewSize = NumBuckets;
+ } else {
+ return;
+ }
+
// Allocate one extra bucket which will always be non-empty. This allows the
// iterators to stop at end.
ItemBucket *NewTableArray =(ItemBucket*)calloc(NewSize+1, sizeof(ItemBucket));