Nouveau - May 2015 - [Bug 90347] New: [NVE0+] Failure to insert texbar under some circumstances (causing bad colors in Terasology)

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

Ilia Mirkin <imirkin at alum.mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from Ilia Mirkin <imirkin at alum.mit.edu> ---
Should be fixed by

commit a2af42c1d2dc91f4c31e25ff9fff15a89a9b6ead
Author: Ilia Mirkin <imirkin at alum.mit.edu>
Date:   Fri Jun 12 16:09:05 2015 +0200

    nvc0/ir: fix collection of first uses for texture barrier insertion

    One of the places we have to insert texbars is in situations where the
    result of the tex gets overwritten by a different instruction (e.g. in a
    conditional statement). However in some situations it can actually
    appear as though the original tex itself is an overwriting instruction.
    This can naturally never really happen, so just ignore the tex
    instruction when it comes up.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90347
    Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
    Cc: "10.5 10.6" <mesa-stable at lists.freedesktop.org>

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