For SPARC-V9, this hap is called when a membar or stbar instruction is executed. For membar, the type contains the 7-bit field cmask|mmask specified in the instruction. For stbar, the type is 8 (equivalent to membar #StoreStore).
For x86, this hap is called when a fence instruction is executed. The type is set from the list provided by the x86_instruction_sync_type_t enum.