18. A method, comprising: determining, by a processor circuit, one or more respective suitability metrics for each of one or more candidate partitioning policies for a set of pixel shader inputs for a graphics frame, each candidate partitioning policy comprising one or more rules for partitioning the set of pixel shader inputs for multi-phase pixel shading based on quality sensitivity values for the pixel shader inputs; selecting a partitioning policy for the set of pixel shader inputs from among the one or more candidate partitioning policies based on the determined suitability metrics; and constructing a multi-phase pixel shader for the graphics frame by partitioning the set of pixel shader inputs into multiple classes according to the selected partitioning policy.
18. A method, comprising: determining, by a processor circuit, one or more respective suitability metrics for each of one or more candidate partitioning policies for a set of pixel shader inputs for a graphics frame, each candidate partitioning policy comprising one or more rules for partitioning the set of pixel shader inputs for multi-phase pixel shading based on quality sensitivity values for the pixel shader inputs; selecting a partitioning policy for the set of pixel shader inputs from among the one or more candidate partitioning policies based on the determined suitability metrics; and constructing a multi-phase pixel shader for the graphics frame by partitioning the set of pixel shader inputs into multiple classes according to the selected partitioning policy. 19. The method of claim 18 , comprising determining a respective quality sensitivity value for each of the set of pixel shader inputs based on an input gradient of that pixel shader input.