"Added DMALLOC_USE_HASHBASE mode" is fe982070cac0283b79a3a4a3a54b7865537acab7.
Also regarding src/pike_memory.c, its history starts with "memory.{c,h} renamed to pike_memory.{c,h}" (4e86f944a018c5397e3c55693b0637f63987e7d7). Regardless of -M, -C and --find-copies-harder flags, I can't see the history past that point.