[Bug 97002] dEQP-GLES3.functional.shaders.derivate.dfdx.fbo_float_vec2_highp fails

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97002

--- Comment #6 from Kenneth Graunke <kenneth at whitecape.org> ---
I agree with Mark.  I don't think we can pass these.  It looks like they were
removed from the mustpass list in:

commit ea026b329e6bf73f109cda914c90f08d5f7a5b8d
Author: Pyry Haulos <phaulos at google.com>
Date:   Tue Jul 21 15:12:53 2015 -0700

    Remove highp float FBO dfd*() tests from mustpass

    Bug: 22628471
    Bug: 22632003
    Change-Id: Ia9d2b9a5e04ad317cbcc8782c9efaeedd94a0a58

Sadly, the commit messages offer no explanation as to why, and I believe those
bug IDs are for a Google-internal bug tracker.  (I suppose we could ask Pyry.)

Having looked around for documentation that could explain the problems, I found
https://hsdes.intel.com/appstore/article/#/1208680029/main
which indicates that the Intel Android team isn't planning on fixing these
tests either.

I found another HSD somewhere which suggested this comes down to numerical
imprecision when interpolating inputs, and that testing dFdx is hard.  I'm
guessing that Skylake must have gotten a little better in that regard; these
tests fail on both Broadwell and Haswell, despite us using the exact same code.

So I don't think we can fix this.  Someone will probably want to follow up with
the WebGL conformance developers and Google developers and remove tests ported
from blacklisted dEQP tests.

Sorry :(

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