1. An apparatus, comprising: logic, at least a portion of which is in hardware, the logic to determine 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, select 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 construct 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.