[Bug 79948] New: [i965] Incorrect pixels when using discard and uniform loads
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Thu Jun 12 11:47:36 PDT 2014
https://bugs.freedesktop.org/show_bug.cgi?id=79948
Priority: medium
Bug ID: 79948
Assignee: idr at freedesktop.org
Summary: [i965] Incorrect pixels when using discard and uniform
loads
QA Contact: intel-3d-bugs at lists.freedesktop.org
Severity: normal
Classification: Unclassified
OS: Linux (All)
Reporter: cody at lunarg.com
Hardware: x86-64 (AMD64)
Status: NEW
Version: git
Component: Drivers/DRI/i965
Product: Mesa
Created attachment 100932
--> https://bugs.freedesktop.org/attachment.cgi?id=100932&action=edit
Patch to piglit test showing the discard problem.
Commit 17c7ead7 exposed a bug in how uniform loading happens in the presence of
discard. It manifested itself in an application as randomly incorrect pixels
on the borders of conditional areas.
We've boiled it down to a piglit test case, attached as a patch to existing
test. When you run it on HSW with mesa 10.2 or later, notice the white line
along the diagonal axis. That shouldn't be there. The white is coming from a
texture sample to make it easy to see the problem. It should have been
multiplied by the uniform values as the rest of the fragments were. The key
bits are in the second fragment shader.
I believe we've root caused it and I'll next attach a fix that I'll send to the
mesa-dev list.
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