An apparatus and method is disclosed for updating a status register in an
out of order execution pipeline. In one embodiment a dispatch unit in a
floating point unit sets a MRI bit flag that indicates that an
instruction is the most recently issued instruction. The dispatch unit
resets the MRI bit flag for all other instructions. Each execution stage
of the execution pipeline keeps track of the MRI bit flag information for
the instruction. A writeback unit updates the status register after the
execution of the instruction that has its MRI bit flag set. The writeback
unit does not update the status register for instructions that have their
MRI bit flag reset. This allows the instruction to be identified that is
the most recent instruction to enter the dispatch unit.