[Nouveau] [Bug 90347] New: [NVE0+] Failure to insert texbar under some circumstances (causing bad colors in Terasology)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90347

            Bug ID: 90347
           Summary: [NVE0+] Failure to insert texbar under some
                    circumstances (causing bad colors in Terasology)
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/nouveau
          Assignee: nouveau at lists.freedesktop.org
          Reporter: imirkin at alum.mit.edu
        QA Contact: nouveau at lists.freedesktop.org

Created attachment 115602
  --> https://bugs.freedesktop.org/attachment.cgi?id=115602&action=edit
terasology.tgsi

The problem is that the attached shader compiles to:

...
 34: mov u32 $r0 $r3 (8)
 35: mov u32 $r1 $r5 (8)
 36: tex 2D $r0 $s0 f32 $r0t $r0d (8)
 37: join mov u32 $r7 $r1 (8)
BB:3 (4 instructions) - idom = BB:0, df = { BB:4 }
 -> BB:4 (forward)
 38: mov u32 $r0 $r3 (8)
 39: mov u32 $r1 $r5 (8)
 40: tex 2D $r1 $s0 f32 $r0t $r0d (8)
 41: join mov u32 $r7 $r1 (8)
...

And there is no texbar before the mov happens. This causes funky rendering in
Terasology.

Somehow things get merged during RA s.t. the findFirstUses logic decides that
the tex itself is a use (it isn't!) and so it never picks up on the actual use
in that BB (since there's a check to make sure that we only pick the earliest
use in a BB). This much shorter shader reproduces a similar issue as well:

FRAG
DCL IN[0], COLOR, COLOR
DCL OUT[0], COLOR
DCL OUT[1], COLOR[1]
DCL SAMP[0]
DCL SAMP[1]
DCL TEMP[0..4], LOCAL
IMM[0] FLT32 {    0.0010,     1.0000,     0.0000,     2.5000}
  5: MOV TEMP[0].xy, IN[0].xyxx
  7: FSLT TEMP[2].x, IMM[0].yyyy, IN[0].xxxx
 10: UIF TEMP[2].xxxx :0
 30:   TEX TEMP[1], TEMP[0], SAMP[0], 2D
 32: ELSE :0
 34:   TEX TEMP[1], TEMP[0], SAMP[1], 2D
 36: ENDIF
 47: UIF TEMP[2].xxxx :0
 50:   MUL TEMP[1], TEMP[1], IMM[0].xyyy
 54: ENDIF
 84: MOV TEMP[0].xyz, TEMP[1].xyzx
 93: MOV TEMP[1].xyz, TEMP[0].wwww
 94: MOV OUT[0], TEMP[0]
 95: MOV OUT[1], TEMP[1]
 97: END

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