[Bug 105826] [Gen7-8] Integer texture views can be incorrect

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Fri Mar 30 23:11:03 UTC 2018


            Bug ID: 105826
           Summary: [Gen7-8] Integer texture views can be incorrect
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/i965
          Assignee: intel-3d-bugs at lists.freedesktop.org
          Reporter: nanleychery at gmail.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

On BDW and earlier, fast-clear colors are limited to 0 and a format-dependent 1
per-channel. For integer textures, the 1 equals 0x1 and for float textures the
1 equals 1.0f (0x3f80000). Due to the clear color value of 1 being interpreted
differently for different formats, it should not be possible to use it without
introducing resolves.

i965 currently allows fast-clearing a float texture to 1 but doesn't introduce
a resolve when accessing the texture as an integer.

We can demonstrate the problem this causes by doing the following:
1. Fast clear an R32F texture to 1.0. For the purpose of this example, we make
it 64x64px.
2. Create an R32UINT texture view from the R32F.
3. Render to the first row of the R32UINT. This will cause the HW to write out
the fast clear color in the parts of the cacheline pairs not written to. Each
CL Pair has a dimension of 8x4px.
4. Read back the texture as R32UINT.
5. Observe that the following 3 rows are equal to 1 instead of the 0x3f800000
it was cleared to in step 1.

We need write a bug to exercise this issue, and then fix it. The piglit test
tests/spec/arb_texture_view/rendering-r32ui.c looks like a good place to start.

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