1. A method comprising: performing shading operations for a pixel set including one or more pixels to generate per-sample shaded attributes according to a shader program executed by a processing pipeline; after generating the per-sample shaded attributes and before z-testing the per-sample shaded attributes, evaluating discard information for the pixel set that is generated during the performance of the shading operations; and before z-testing the per-sample shaded attributes, discarding one or more per-sample shaded attributes for at least one pixel in the pixel set based on the evaluated discard information.