An apparatus for processing data 2 is provided including processing circuitry 24 controlled by an instruction decoder 20 in response to a stream of program instructions. There is also provided dedicated function hardware 12 configured to receive output data from the processing circuitry and to perform a dedicated processing operation. The instruction decoder 20 is responsive to an end instruction 54 and a software processing flag (blend_shade_enabled) to control the processing circuitry to end a current software routine, to generate output data and in dependence upon the software processing flag either trigger processing of the output data by the dedicated function hardware or trigger the processing circuitry to perform a further software routine upon the output data to generate software generated result data instead of hardware generated result data as generated by the dedicated hardware circuitry.