[Bug 47201] New: TGSI source register with absolute negative modifier does not work correctly

[Bug 47201] New: TGSI source register with absolute negative modifier does not work correctly

[bugzilla-daemon]

https://bugs.freedesktop.org/show_bug.cgi?id=47201

             Bug #: 47201
           Summary: TGSI source register with absolute negative modifier
                    does not work correctly
    Classification: Unclassified
           Product: Mesa
           Version: 8.0
          Platform: Other
        OS/Version: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/Gallium/r600
        AssignedTo: dri-devel@lists.freedesktop.org
        ReportedBy: llyzs@163.com


Recently I found a TGSI fragment shader does not render correctly with r600
driver and I further identified the issue down to instructions in this form:

CMP TEMP[0].yz, -|TEMP[1].xxxx|, TEMP[2].xxxx, CONST[0].xyxw

If I covert all those instructions to the equivalents:

ABS TEMP[5], TEMP[1].xxxx
CMP TEMP[0].yz, -TEMP[5], TEMP[2].xxxx, CONST[0].xyxw

It then works fine. However, the original instructions work just fine with
nouveau and swrast driver, so it should be a r600 bug. Any clue on this issue?

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

--- Comment #1 from Vic Lee <llyzs@163.com> 2012-03-11 06:24:37 UTC ---
The issue might be related to r600_bytecode_alu_build() in r600_asm.c. In the
codes below:

    if (alu->is_op3) {
        // in this code branch it does not use absolute modifier at all.
    } else {
    ...

Looks like whenever is_op3 is true (which is the case of CMP), absolute
modifier is just ignored.

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

Vic Lee <llyzs@163.com> changed:

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

--- Comment #2 from Vic Lee <llyzs@163.com> 2012-03-11 06:47:32 UTC ---
OK I found the reference info in r600 instruction document and this is a
hardware limitation. So this probably has to be solved in higher level rather
than in driver.

Sorry for the noise.

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

Vic Lee <llyzs@163.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|TGSI source register with   |Absolute modifier does not
                   |absolute negative modifier  |work with 3-source TGSI
                   |does not work correctly     |instructions

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

Tom Stellard <tstellar@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|NOTABUG                     |

--- Comment #3 from Tom Stellard <tstellar@gmail.com> 2012-03-11 18:07:27 PDT ---
The is a bug in the r600 driver.  The shader compiler should be lowering this
to the hardware equivalent of this sequence:

ABS TEMP[5], TEMP[1].xxxx
CMP TEMP[0].yz, -TEMP[5], TEMP[2].xxxx, CONST[0].xyxw

Is there a piglit test or application that is hitting this bug?

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

--- Comment #4 from Vic Lee <llyzs@163.com> 2012-03-12 06:33:54 PDT ---
Thanks for concerning this bug. It will be great if this can be fixed at driver
level. I created a smallest possible test program which will be able to test
the shader I am having problem with.

Please see the file header for test info.

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

--- Comment #5 from Vic Lee <llyzs@163.com> 2012-03-12 06:34:57 PDT ---
Created attachment 58317
  --> https://bugs.freedesktop.org/attachment.cgi?id=58317
test program to reproduce the bug

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

--- Comment #6 from xbx <xavierb@gmail.com> ---
Created attachment 112920
  --> https://bugs.freedesktop.org/attachment.cgi?id=112920&action=edit
r600g patch to fix dropped abs() modifier on op3 alu operations.

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

--- Comment #7 from xbx <xavierb@gmail.com> ---
I stumbled upon this bug while testing and debugging a game using the st/nine.

And I made a tentative fix that works for me. 
(caveat: I know nothing about mesa/gallium/graphic cards, but hey..)

Here is the proposed patch:

https://github.com/xxxbxxx/Mesa-3D/commit/0722d721f8e5ec496bf8ce4591a3b8a5bf87745d

or attached.

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[Bug 47201] Absolute modifier does not work with 3-source TGSI instructions

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https://bugs.freedesktop.org/show_bug.cgi?id=47201

Gert Wollny <gw.fossdev@gmail.com> changed:

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

--- Comment #8 from Gert Wollny <gw.fossdev@gmail.com> ---
This was fixed with ad84689f737edefe.

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