The invention provides a method of compiling computer program instructions for implementation on a reconfigurable processor comprising a plurality of operational cells, each operational cell being connectable to and disconnectable from one or more of the other operational cells via a programmable interconnect, the method comprising: a routing step in which one or more signal processing paths are determined for performing one or more signal processing operations defined by the computer program instructions, each signal processing path comprising two or more of the operational cells connected via the programmable interconnect, the said signal processing paths being capable of implementation on the said operational cells and the said interconnect of the reconfigurable processor to perform the said one or more signal processing operations; and a post-routing step performed subsequent to the routing step in which an extended signal processing path is determined by extending one of the said signal processing paths determined in the routing step such that a critical path of the extended signal processing path is longer than a longest critical path of the signal processing paths determined in the routing step.