Bug 110305

Summary: Iris driver fails ext_packed_depth_stencil-getteximage test
Product: Mesa Reporter: asimiklit <andrey.simiklit>
Component: Drivers/Gallium/IrisAssignee: Intel 3D Bugs Mailing List <intel-3d-bugs>
Status: RESOLVED FIXED QA Contact: Intel 3D Bugs Mailing List <intel-3d-bugs>
Severity: normal    
Priority: medium    
Version: git   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:

Description asimiklit 2019-04-02 08:59:12 UTC 
It fails on a FLOAT_32_UNSIGNED_INT_24_8_REV format
Stencil values which were recorded by a glTexImage2D are not
equal to the stencil values which were received by a glGetTexImage
https://gitlab.freedesktop.org/mesa/piglit/blob/master/tests/spec/ext_packed_depth_stencil/getteximage.c#L131

The result examples for a 8-bit stencil:
i965:
+--------------------+-----------+
|Expected pixel value|Pixel value|
+--------------------+-----------+
|     0x000000a3     | 0x000000a3|
|     0x000000a2     | 0x000000a2|
|     0x000000a1     | 0x000000a1|
|     0x000000a0     | 0x000000a0|
|     0x0000009f     | 0x0000009f|
|     0x0000009e     | 0x0000009e|
+--------------------+-----------+

iris:
+--------------------+-----------+
|Expected pixel value|Pixel value|
+--------------------+-----------+
|     0x000000a3     | 0x000055a3|
|     0x000000a2     | 0x000055a2|
|     0x000000a1     | 0x000000a1|
|     0x000000a0     | 0x000000a0|
|     0x0000009f     | 0x3ec2c29f|
|     0x0000009e     | 0x3ec6c69e|
+--------------------+-----------+

Note: gallium doesn't clean an unused space here (but I guess that it is an expected behavior):
https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/gallium/auxiliary/util/u_transfer_helper.c#L276-301

Actually I guess that it is rather a piglit test issue because spec saying
about FLOAT_32_UNSIGNED_INT_24_8_REV the following:

+---------------+------------+---+
| 1st component |   Unused   |2nd|
+---------------+------------+---+
     32-bit        24-bit     8-bit

I actually guess that "unused" means that there is no guarantee that it
must be clean but I am not sure whether it enough for mesa or I should find
some more strict wording about it.

So possible piglit test fix is:
   -if (buf[i*2+1] != tex[i*2+1]) {
   +if ((buf[i*2+1] & 0xffu) != tex[i*2+1]) {
Comment 1 asimiklit 2019-04-03 13:12:18 UTC 
I created an MR for this issue:
https://gitlab.freedesktop.org/mesa/piglit/merge_requests/32

And some clarification question on Khronos gitlab:
https://github.com/KhronosGroup/OpenGL-API/issues/48

I will create a MR for mesa/gallium as was suggested by Eric Anholt <eric@anholt.net>
Comment 2 asimiklit 2019-04-23 10:12:21 UTC 
Fixed by a commit: cade9001b1758ee9b76f365b02822c97a414006a

This is a field of FLOAT_32_UNSIGNED_INT_24_8_REV texture pixel.
OpenGL spec "8.4.4.2 Special Interpretations" is saying:
   "the second word contains a packed 24-bit unused field,
    followed by an 8-bit index"
The spec doesn't require us to clear this unused field
however it make sense to do it to avoid some
undefined behavior in some apps.

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