<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - Regression in Mesa 17 on s390x (zSystems)" href="https://bugs.freedesktop.org/show_bug.cgi?id=100613#c45">Comment # 45</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - Regression in Mesa 17 on s390x (zSystems)" href="https://bugs.freedesktop.org/show_bug.cgi?id=100613">bug 100613</a> from <a class="email" href="mailto:sroland@vmware.com" title="Roland Scheidegger <sroland@vmware.com>"> Roland Scheidegger</a> <pre>(In reply to Ben Crocker from <a href="show_bug.cgi?id=100613#c44">comment #44</a>) > By the way, draw-vertices-2101010 is failing across all architectures: > X86 and PPC64LE as well as PPC64/S390x. Yes, but this isn't related to swizzling (at least on x86, unless ppc64 has additional errors), but is rather due to GL weirdness with converting signed numbers. Pre-GL 4.2 there's 2 different formulas depending on if it's used as a vertex format or a pixel format, and the test expects the result of the formula used for vertex formats. GL 4.2 and up ditched this formula entirely (obviously, two formulas don't make all that much sense if pixel and vertex data is all in the same buffers anyway...), and that's the one we always use, no matter the GL version. The difference in the formulas usually isn't all that large, but with just 2 bits the error is huge: the four values you can represent are [-1.0, -0.333, 0.333, 1.0] for the old formula and [-1.0, -1.0, 0.0, 1.0] for the new one, hence the failure (Expected: ... 0.333000, Observed: ... 0.000000). Note that at least some hw/drivers will ignore these old GL rules too (after all, GL 4.2 is supposed to be backwards compatible, and clearly with the different formula gone it can't quite be), therefore we don't consider this a driver bug, rather a test bug: <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - [HSW Bisected]Piglit spec/ARB_vertex_type_2_10_10_10_rev/draw-vertices-2101010 fails" href="show_bug.cgi?id=59150">https://bugs.freedesktop.org/show_bug.cgi?id=59150</a></pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>