1. A data execution unit comprising: an arithmetic unit (AU) for performing selected operations on first and second operands in one of a plurality of arithmetic formats and providing a resultant thereof; an arithmetic unit control coupled to the arithmetic unit for selectively controlling the operation to be performed by said AU; first means for providing said first operand to said arithmetic unit in response to an operand selection portion of an instruction; second means for providing the second operand to said arithmetic unit, said second means providing the second operand to said arithmetic unit in response to the same operand selection portion of the instruction; and third means for providing a third operand to said arithmetic unit in response to the same operand selection portion of the instruction, said third operand being used by the arithmetic unit control to select one of the plurality of arithmetic formats.