[Bug 91114] ES3-CTS.gtf.GL3Tests.shadow.shadow_execution_vert fails

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91114

--- Comment #12 from Iago Toral <itoral at igalia.com> ---
I don't see anything special in the generated IR. After my patch we change the
way we compute the lod by subtracting 1 unit, but that is expected as per the
commit log. The test itself does not seem to do weird things either after a
quick glance at it.

I am wondering if the problem may spawn from rounding issues so that depending
on the specific test we are doing sometimes we fall on the wrong side of the
rounding. While I was working on deqp I noticed that the problem was that we
were computing a wrong value of LOD in all the scenarios and verified that
subtracting 1.0 from the computed LOD fixed the problem, but as I explain in
the commit log, I am not sure why this is needed. That change seemed consistent
with the way in which deqp computed the expected result for those tests but
maybe we do not need to subtract 1.0 to get the lod we need, maybe the problem
that deqp detected was a rounding issue and by removing 1.0 we just fell on the
right side of the rounding for those tests. I have just checked that for
piglit, it is enough if we subtract 0.51.

Tapani, could you replace my -1.0 addition by -0.51 and see if that fixes the
CTS test? In parallel, I'll check if this is also enough for dEQP.

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