[Bug 78648] Texture artifacts in Kerbal Space Program

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=78648

--- Comment #4 from Matt Turner <mattst88 at gmail.com> ---
Created attachment 99539
  --> https://bugs.freedesktop.org/attachment.cgi?id=99539&action=edit
49.diff

Reverting the commit and comparing shader disassembly doesn't show me anything
plausible. Reverting the patch causes the code to change in shaders 49 and 52
(and their duplicates 103 and 106, respectively).

The changes are just rescheduling some cmp instructions with null destinations,
like

-cmp.l.f0(16) null      g24<8,8,1>D  30D                       { align1
WE_normal 1H switch };
 mad(16)      g4<1>     g42<4,4,1>F  g74<4,4,1>F  g36<4,4,1>F  { align16
WE_normal 1H };
 send(16)     g16<1>UW  g2<8,8,1>F
                        sampler (1, 0, 0, 2) mlen 4 rlen 8     { align1
WE_normal 1H };
+cmp.l.f0(16) null      g24<8,8,1>D  30D                       { align1
WE_normal 1H switch };

cmp's source is never touched in the interval in which it moves. The flag
register also isn't read or written. At first I thought the send might write
g24 but it just writes g16-g23.

Can you confirm that reverting the patch fixes the problem? Did running the
game (when you captured the shaders) demonstrate the problem? If not, we might
not have found the broken shader yet.

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