System, method, and computer program product for discarding pixel samples

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.

2. The method of claim 1 , wherein the discard information indicates that all samples in the pixel set should be discarded.

3. The method of claim 1 , wherein the discard information comprises a kill mask that is generated for the pixel set by the processing pipeline when a discard instruction is executed.

4. The method of claim 3 , wherein the kill mask includes a bit for each pixel in the pixel set.

5. The method of claim 1 , wherein the discard information comprises a shader mask that is computed for the pixel set by the processing pipeline during the shading operations.

6. The method of claim 5 , wherein the shader mask includes a bit for each sample in the pixel set.

7. The method of claim 5 , wherein the discard information comprises results of a texture colorKey operation.

8. The method of claim 7 , wherein the at least one pixel is discarded immediately after a filtered texture value is generated for each sample of the at least one pixel.

9. The method of claim 5 , wherein evaluating the discard information comprises:

determining that generation of the shader mask is enabled for the shader program; and

fetching the shader mask.

10. The method of claim 1 , wherein each pixel in the pixel set includes at least two samples.

11. The method of claim 1 , further comprising fetching the per-sample shaded attributes for any pixels in the pixel set that are not discarded based on the evaluated discard information.

12. A system comprising:

a processing pipeline that is configured to:

perform 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;

evaluate discard information for the pixel set after the per-sample shaded attributes are generated and before z-testing the per-sample shaded attributes, where the discard information is generated during the performance of the shading operations; and

before z-testing the per-sample shaded attributes, discard one or more per-sample shaded attributes for at least one pixel in the pixel set based on the evaluated discard information.

13. The system of claim 12 , wherein the discard information indicates that all samples in the pixel set should be discarded.

14. The system of claim 12 , wherein the discard information comprises a kill mask that is computed for the pixel set by the processing pipeline when a discard instruction is executed.

15. The system of claim 14 , wherein the kill mask includes a bit for each pixel in the pixel set.

16. The system of claim 12 , wherein the discard information comprises a shader mask that is computed for the pixel set by the processing pipeline during the shading operations.

17. The system of claim 16 , wherein the shader mask includes a bit for each sample in the pixel set.

18. The system of claim 16 , wherein the discard information comprises results of a texture colorKey operation.

19. The system of claim 18 , wherein the at least one pixel is discarded immediately after a filtered texture value is generated for each sample of the at least one pixel.

20. A non-transitory computer-readable storage medium storing instructions that, when executed by a processor, causes the processor to perform steps 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.