<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body><a class="email" href="mailto:apinheiro@igalia.com" title="Alejandro Piñeiro (freenode IRC: apinheiro) <apinheiro@igalia.com>"> Alejandro Piñeiro (freenode IRC: apinheiro)</a> changed <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> <table border="1" cellspacing="0" cellpadding="8"> <tr> <th>What</th> <th>Removed</th> <th>Added</th> </tr> <tr> <td style="text-align:right;">CC</td> <td> </td> <td>apinheiro@igalia.com </td> </tr></table> <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#c9">Comment # 9</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:apinheiro@igalia.com" title="Alejandro Piñeiro (freenode IRC: apinheiro) <apinheiro@igalia.com>"> Alejandro Piñeiro (freenode IRC: apinheiro)</a> <pre>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] > 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/tests/spec/arb_fake/execution/ubo/matrix-column-vs-row.shader_test">https://github.com/Igalia/piglit/blob/apinheiro/matrix-row-major-failure/tests/spec/arb_fake/execution/ubo/matrix-column-vs-row.shader_test</a> or in a ideal world, get the script to be configurable on how many tests to create, and the default being a reasonable amount of tests (fwiw, 540 generated tests seems somewhat too much). > 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? Unfourtunately although I would be interested on working on this, I don't have the time right now. And now totally off-topic, but probably it is worth to mention here to not forget: VK-GL-CTS doesn't catch this problem either. And they have tons of row_major tests, for example: KHR-GL45.shaders.uniform_block.single_basic_type.std140.row_major_mediump_mat4 is passing properly. So or the test is wrong or it is incomplete. I tried to take a look to the test, but it is somewhat hard to understand. <a href="https://github.com/KhronosGroup/VK-GL-CTS/blob/master/external/openglcts/modules/common/glcUniformBlockCase.cpp#L1346">https://github.com/KhronosGroup/VK-GL-CTS/blob/master/external/openglcts/modules/common/glcUniformBlockCase.cpp#L1346</a></pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>