1. A method of operating a graphics processing system, the graphics processing system including: a graphics processing pipeline comprising a programmable processing stage that executes programs to perform graphics processing operations when generating an output of the graphics processing pipeline; and processing circuitry that is operable to convert a program provided for execution by the programmable processing stage of the graphics processing pipeline to a program to be executed by the programmable processing stage of the graphics processing pipeline; the method comprising: the processing circuitry: determining for a program provided for execution by the programmable processing stage of the graphics processing pipeline, whether the program relates to performing multi-view rendering to render a set of plural images representing plural different views of the same scene; and, when it is determined that the program relates to performing multi-view rendering to render a set of plural images representing plural different views of the same scene, at least one of: (i) determining whether the program includes a processing operation that can be performed only once for the set of plural views of the scene that are being rendered; and when it is determined that the program includes a processing operation that can be performed only once for the set of plural views of the scene that are being rendered, including in a program to be executed by the programmable processing stage of the graphics processing pipeline, a sequence of at least one graphics program instruction that when executed will cause the programmable processing stage of the graphics processing pipeline to perform that processing operation for a work item once for the set of plural views of the scene that are being rendered and to provide only a single output value for a work item for that processing operation for the set of views; and (ii) determining whether the program includes a processing operation that should be performed separately for each view of the set of plural views of the scene that are being rendered; and when it is determined that the program includes a processing operation that should be performed separately for each view of the set of plural views of the scene that are being rendered, including in the program to be executed by the programmable processing stage of the graphics processing pipeline, a sequence of at least one graphics program instruction that when executed will cause the programmable processing stage of the graphics processing pipeline to perform that processing operation for a work item separately for each view of the set of plural views of the scene that are being rendered, so as to provide a separate output value for a work item for that processing operation for each view of the set of views; the method further comprising: providing the program to the graphics processing pipeline for execution; and the programmable processing stage of the graphics processing pipeline when it is to perform processing operations for work items to be processed for the set of plural views to be rendered, executing the program once for each work item to be processed; wherein the executing the program for a work item comprises, in response to the instructions in the program, at least one of: (i) when the program provided to the graphics processing pipeline for execution comprises a sequence of at least one graphics program instruction that when executed will cause the programmable processing stage of the graphics processing pipeline to perform a processing operation for a work item once for the set of plural views of the scene that are being rendered and to provide only a single output value for a work item for that processing operation for the set of views, performing that processing operation for the work item once for the set of plural views of the scene that are being rendered and providing only a single output value for the work item for that processing operation for the set of views; and (ii) when the program provided to the graphics processing pipeline for execution comprises a sequence of at least one graphics program instruction that when executed will cause the programmable processing stage of the graphics processing pipeline to perform a processing operation for a work item separately for each view of the set of plural views of the scene that are being rendered, so as to provide a separate output value for a work item for that processing operation for each view of the set of views, performing that processing operation for the work item separately for each view of the set of plural views, so as to provide a separate output value for that processing operation for the work item for each view of the set of plural views that are being rendered.