<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - mat4: m[i][j] incorrect result with row_major UBO" href="https://bugs.freedesktop.org/show_bug.cgi?id=104553#c10">Comment # 10</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - mat4: m[i][j] incorrect result with row_major UBO" href="https://bugs.freedesktop.org/show_bug.cgi?id=104553">bug 104553</a> from <a class="email" href="mailto:t_arceri@yahoo.com.au" title="Timothy Arceri <t_arceri@yahoo.com.au>"> Timothy Arceri</a> <pre>(In reply to Alejandro Piñeiro (freenode IRC: apinheiro) from <a href="show_bug.cgi?id=104553#c9">comment #9</a>) > Found this bug when I was about to report the same problem. Some comments > below: > > (In reply to florian.will from <a href="show_bug.cgi?id=104553#c0">comment #0</a>) > > Created <a href="attachment.cgi?id=136630" name="attach_136630" title="Failing piglit test (when test_variant = 2) for this bug.">attachment 136630</a> <a href="attachment.cgi?id=136630&action=edit" title="Failing piglit test (when test_variant = 2) for this bug.">[details]</a> > > Failing piglit test (when test_variant = 2) for this bug. > > > > I hit another bug while trying to get Banshee 3D > > <<a href="https://github.com/BearishSun/BansheeEngine">https://github.com/BearishSun/BansheeEngine</a>> to work correctly on Mesa > > radeonsi (HD 7870) / amdgpu kernel module. I use git commit 2719467eb6 right > > now, which is a few days old. > > > > Accessing a "mat4 m" component, e.g. m[1][2], returns unexpected results if > > m is declared inside a UBO block and uses row_major matrix format. col_major > > works as expected. m[1].z also works. Some experiments indicate that for > > m[i][j], the UBO buffer is accessed at offset (i+j)*4 instead of (i+j*4)*4. > > > > The invalid offsets for loading floats from the UBO are visible in the Mesa > > IR when linker.cpp is done (probably introduced by lower_ubo_reference()). > > As you imply below, this problem also affects ssbo. So perhaps it would be a > good idea to update the bug description? > > > While exploring this issue, I prepared a piglit test case that tests for > > this. It fails on my setup (when test_variant = 2, the other tests succeed). > > I will attach it to this bug report and send it to the piglit list for > > review. > > > > > > > > Possible Fix: > > > > I doubt this is enough/correct, because I haven't fully grasped the IR > > processing in the glsl compiler and which fields/data types can/can't be > > row_major and the implications, but this simple change in > > lower_buffer_access.cpp > > FWIW, while I was doing a skimming, I also got to lower_buffer_access and > lower_ubo_reference (this one touches both ssbo and ubo), so I agree that > the issue is likely at that code. Not sure if your fix is correct or in the > good path sorry. > > (In reply to florian.will from <a href="show_bug.cgi?id=104553#c7">comment #7</a>) > > Created <a href="attachment.cgi?id=136878" name="attach_136878" title="Changes to piglit UBO test generator">attachment 136878</a> <a href="attachment.cgi?id=136878&action=edit" title="Changes to piglit UBO test generator">[details]</a> <a href='page.cgi?id=splinter.html&bug=104553&attachment=136878'>[review]</a> [review] [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. > > Somewhat off-topic: Timothy mentioned that in the past it was not included > due all the amount of tests added. So perhaps a compromise would be added > some (~10?) barebone tests, to at least cover the most basic cases. > Something like this test I wrote while debugging this: > <a href="https://github.com/Igalia/piglit/blob/apinheiro/matrix-row-major-failure/">https://github.com/Igalia/piglit/blob/apinheiro/matrix-row-major-failure/</a> > tests/spec/arb_fake/execution/ubo/matrix-column-vs-row.shader_test > Yes for now I'd be happy with someone committing a piglit test that trips up the bug. Please go ahead and push your test as its the simplest of the two tests. Thanks.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> </ul> </body> </html>