<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - Shadertoy shader causing hang" href="https://bugs.freedesktop.org/show_bug.cgi?id=111241#c6">Comment # 6</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - Shadertoy shader causing hang" href="https://bugs.freedesktop.org/show_bug.cgi?id=111241">bug 111241</a> from <a class="email" href="mailto:pierre-eric.pelloux-prayer@amd.com" title="Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>"> Pierre-Eric Pelloux-Prayer</a> <pre>I've created a different shadertoy showing the problem: <a href="https://www.shadertoy.com/view/Wt2SW1">https://www.shadertoy.com/view/Wt2SW1</a> (but this one doesn't hang the GPU). The shader for "Buffer A" is: 0: MOV TEMP[0], SV[0] 1: MAD TEMP[0].y, SV[0], CONST[0][2].xxxx, CONST[0][2].yyyy 2: MOV OUT[0], IMM[0].xxxx 3: USEQ TEMP[1].x, CONST[0][1].xxxx, IMM[1].xxxx 4: UIF TEMP[1].xxxx 5: ADD TEMP[2], TEMP[2], -TEMP[2] 6: ELSE [...] 13: MOV OUT[0], TEMP[2] 14: END TEMP[2] is used before being assigned a value, so I suppose that's what allows LLVM to turn line 5 in: v_mov_b32_e32 v3, 0x7fc00000 v_mov_b32_e32 v2, 0x7fc00000 v_mov_b32_e32 v1, 0x7fc00000 v_mov_b32_e32 v0, 0x7fc00000 (ie: output is NaN) A possible way to fix this is to transform "dst = x - x" operations in "dst = 0" which is what nir does in its nir_opt_algebraic pass. I've open a MR to fix/discuss this issue: <a href="https://gitlab.freedesktop.org/mesa/mesa/merge_requests/1681">https://gitlab.freedesktop.org/mesa/mesa/merge_requests/1681</a></pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the assignee for the bug.</li> </ul> </body> </html>