[Bug 97083] [IVB,BYT] GPU hang on deqp-gles31.functional.separate.shader.random

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97083

Kenneth Graunke <kenneth at whitecape.org> changed:

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

--- Comment #2 from Kenneth Graunke <kenneth at whitecape.org> ---
Curro figured this one out.  The problem was the NoDDClear/NoDDCheck flags on
the PLN instructions.  Normally, we do a (-f0.0) PLN with NoDDClear (for helper
pixels) and a (+f0.0) PLN with NoDDCheck.  This works fine at the top level,
because at least one pixel won't be a helper invocation, so the (-f0.0) PLN
with NoDDClear will actually execute.

But with my (broken) rework, we started emitting PLNs inside control flow.  If
only helper pixels take a certain control flow path, the (-f0.0) PLN with
NoDDClear might not ever execute, leaving the register dependency set, so the
next instruction that tries to touch that register would hang.

So, move to top is a real solution to this problem, not just papering over it.
I've also sent a patch to the mailing list that eliminates the PLN dependency
hints, which will allow us to move PLNs into control flow safely (if we want
to):
https://lists.freedesktop.org/archives/mesa-dev/2016-August/124946.html

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-3d-bugs/attachments/20160802/c4b2a390/attachment-0001.html>