Data processing apparatus and method for processing a received workload in order to generate result data

A data processing apparatus and method are provided for processing a received workload in order to generate result data. A thread group generator generates from the received workload a plurality of thread groups to be executed to process the received workload. Each thread may be either an active thread whose output is required to form the result data, or a dummy thread required to resolve the inter-thread dependency for one of the active threads but whose output is not required to form the result data. Execution flow modification circuitry is responsive to the received thread group having at least one dummy thread, to cause the thread execution unit to selectively omit at least part of the execution of at least one of the plurality of instructions when executing each dummy thread, in dependence on control information associated with the predetermined program.