A data processor includes an execution unit that executes instructions to perform data processing operations, a register file operable to store data values for use by and produced by the execution unit, and a buffer intermediate between the register file for providing data values from the register file to the execution unit for use when executing an instruction, and to receive output data values from the execution unit for writing to the register file.
Instructions to be executed by the execution unit of the data processor have associated buffer eviction priority indications representative of a priority for eviction from the buffer of an output data value that will be generated when executing the instruction. The buffer eviction priority indications are then used when selecting data values to evict from the buffer.