Created attachment 136878 [details] [review]
Changes to piglit UBO test generator

I have now extended the random UBO piglit test generator python script (in a
hackish way) to generate SSBO tests as well, and added std430 packing rules to
generate std430 SSBO tests. My changes are in the attached patch file, but I'd
say it's not suitable for piglit git (too ugly).

It was helpful to validate the mesa patch I've attached to this bug report
earlier. Using mesa git master, 391 out of the 540 generated UBO&SSBO tests
fail. After applying my patch, only a few tests (3-7) fail. The failing tests
are always very huge test files (some have more than 10k lines and sometimes up
to 5MB shader_test files). Apparently they hit something like an internal size
limit for vertex shaders, because the tests pass when commenting out one half
of the test conditions in the vertex shader, and they still pass when
commenting out the other half of the vertex shader.

So I'm now fairly confident that my patch improves the SSBO / UBO buffer access
behaviour when reading from SSBOs and UBOs.

Is there anything else that should be tested? Or any comments about the patch
by someone who knows the lower_buffer_access code better than I do?