In mesa CI, about 10% of test runs generate a single failure in the subgroups category. A quick look at the history shows the following failures:
Typical output for a failure:
1022 / 1023 values passed
All tests in the recent CI history occure on GT3e systems, even though nearly half of the BDW in CI are GT2.
Looking into this deeper, I really don't think it has anything to do with subgroups. Instead, I suspect that the issue here has something to do with SSBO stores from graphics shader stages. I dug through the bspec and couldn't find anything GT3 specific.
-- GitLab Migration Automatic Message --
This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.
You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/mesa/mesa/issues/1791.