I found that the OpenGL saying: OpenGL spec: "5.3.3 Rules ....... Note: “Updates” via rendering or transform feedback are treated consistently with updates via GL commands. Once EndTransformFeedback has been issued, any subsequent command in the same context that uses the results of the transform feedback operation will see the results." i965 makes the several cache invalidations (VF, L3, ...) in EndTransformFeedback function to make the streamout result visible for others but unfortunately Iris doesn't do it. I will provide a solution for this issue shortly.
Suggested solution: https://gitlab.freedesktop.org/mesa/mesa/merge_requests/635
Should be fixed: commit 4e9592c5fa249df11d9aab665f49f26f3d428d77 Author: Andrii Simiklit <andrii.simiklit@globallogic.com> Date: Thu Apr 25 11:19:46 2019 +0300 iris: make the TFB result visible to others
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