Merging narrow register for resolution of data dependencies when updating a portion of a register in a microprocessor

摘要

A microprocessor includes general purpose registers which may be accessed or updated in portions. Dependencies may be created between an instruction which updates only a portion of a destination register and a subsequent instruction which requires a larger portion of that destination register, inclusive of the smaller updated portion, as a source. To resolve such dependencies between instructions, a determination is made upon decode of an instruction whether it updates only a portion of a destination or the entire destination. If only a portion of the destination is updated by the instruction, a read of the destination is done prior to execution of the instruction and the data read from the destination is merged with the results of the instruction execution. The merged data is then conveyed as the results of the instruction execution.