[Bug 89637] New: dEQP-GLES3: atan, atan2, do not have enough precision

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89637

            Bug ID: 89637
           Summary: dEQP-GLES3: atan, atan2, do not have enough precision
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/DRI/i965
          Assignee: idr at freedesktop.org
          Reporter: itoral at igalia.com
        QA Contact: intel-3d-bugs at lists.freedesktop.org

List of affected tests:

dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_vertex.scalar
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_vertex.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_vertex.vec3
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_vertex.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_fragment.scalar
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_fragment.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_fragment.vec3
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.lowp_fragment.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.mediump_vertex.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.mediump_vertex.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.mediump_fragment.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.mediump_fragment.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_vertex.scalar
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_vertex.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_vertex.vec3
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_vertex.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_fragment.scalar
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_fragment.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_fragment.vec3
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan2.highp_fragment.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_vertex.scalar
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_vertex.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_vertex.vec3
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_vertex.vec4
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_fragment.scalar
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_fragment.vec2
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_fragment.vec3
dEQP-GLES3.functional.shaders.builtin_functions.precision.atan.highp_fragment.vec4

According to the GLES3 specs, trigonometric functions have undefined precision,
so I wonder if these tests are valid at all.

Since these are approximated using polynomials, in case we want to improve
precision, we could use higher order polynomials at the cost of some
performance. I have conducted some tests after a quick research and found some
polynomials that seemed to reduce significantly the number of tests failed (for
combined highp, mediump, lowp tests) but increased significantly the maximum
absolute error we obtained in some cases, so we probably want to find better
polynomials if we want to improve this.

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