<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [ANV] The Witcher 3 shadows flickering" href="https://bugs.freedesktop.org/show_bug.cgi?id=109404#c19">Comment # 19</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [ANV] The Witcher 3 shadows flickering" href="https://bugs.freedesktop.org/show_bug.cgi?id=109404">bug 109404</a> from <a class="email" href="mailto:mattst88@gmail.com" title="Matt Turner <mattst88@gmail.com>"> Matt Turner</a> <pre>(In reply to Danylo from <a href="show_bug.cgi?id=109404#c18">comment #18</a>) > What have I found on Friday: > > The NIR I have attached is not a problem - it's a correct one as Jason > corrected me on IRC. > > The issue seems to be even further down, in native code such comparison > generated: > > asr.le.f0.0(8) null<1>D -g0<0,1,0>W 15D { align1 1Q > }; > > ... > > (+f0.0) if(8) JIP: 128 UIP: 128 { align1 1Q > }; > > The 15th bit of that register means: > > 0: Front Facing > 1: Back Facing > > Then it is negated to have: > > 0: Back Facing > ~0: Front Facing > > Then the *signed* .le (less or equal) with zero, as I see it - this is the > wrong part, ~0 < 0 when comparison is signed however the initial intention > was to have "false" in this comparison when triangle is front facing. > > Manually changing null<1>D to null<1>UD fixes the issue. > > How such comparison is created? > > brw_fs_cmod_propagation.cpp, in opt_cmod_propagation_local, line 323 - > CONDITION_LE modifier is propagated when condition operates on two > REGISTER_TYPE_UD while scan_inst (opcode: asr) has dst: REGISTER_TYPE_D and > src: REGISTER_TYPE_W. > > From my point of view it's not a correct thing to do, but I'm not sure what > to do here. I'm just (In reply to Danylo from <a href="show_bug.cgi?id=109404#c18">comment #18</a>) > What have I found on Friday: > > The NIR I have attached is not a problem - it's a correct one as Jason > corrected me on IRC. > > The issue seems to be even further down, in native code such comparison > generated: > > asr.le.f0.0(8) null<1>D -g0<0,1,0>W 15D { align1 1Q > }; > > ... > > (+f0.0) if(8) JIP: 128 UIP: 128 { align1 1Q > }; > > The 15th bit of that register means: > > 0: Front Facing > 1: Back Facing > > Then it is negated to have: > > 0: Back Facing > ~0: Front Facing > > Then the *signed* .le (less or equal) with zero, as I see it - this is the > wrong part, ~0 < 0 when comparison is signed however the initial intention > was to have "false" in this comparison when triangle is front facing. > > Manually changing null<1>D to null<1>UD fixes the issue. > > How such comparison is created? > > brw_fs_cmod_propagation.cpp, in opt_cmod_propagation_local, line 323 - > CONDITION_LE modifier is propagated when condition operates on two > REGISTER_TYPE_UD while scan_inst (opcode: asr) has dst: REGISTER_TYPE_D and > src: REGISTER_TYPE_W. > > From my point of view it's not a correct thing to do, but I'm not sure what > to do here. Thank you very much for the analysis (and attaching the shader). I'll take a closer look.</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>