a common usage for hash tables is for tracking exactly one instance of a pointer for a given period of time, after which the table's entries are purged and it is reused this macro enables the purge phase of such usage to reset the table to a pristine state, avoiding future rehashing due to ballooning of deleted entries Reviewed-by: Adam Jackson <ajax@redhat.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8498>