A programmable processor and method for improving the performance of
processors by incorporating an execution unit operable to decode and
execute single instructions specifying both a mask and a register
containing data, the mask comprising fields that each correspond to a
field of the data contained in the register, the execution unit is
operable to detect some of the fields of the mask as having a
predetermined value and identifying corresponding fields of the data
contained in the register as write-enabled data fields; and cause the
write-enabled data fields to be written to a specified memory location.