[Piglit] [PATCH] glsl: update assumption in array out of bounds test

[Nicolai Hähnle]

On 31.03.2017 01:53, Timothy Arceri wrote:
> Section 5.7 of the GLSL 4.5 spec says:
>
>    "Behavior is undefined if a shader subscripts an array with an
>    index less than 0 or greater than or equal to the size the array
>    was declared with."
>
> So we cannot be sure which path the shader will take. Update the
> test so that both branches end in the same result.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=96684
> ---
>  tests/shaders/glsl-array-bounds-01.shader_test | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tests/shaders/glsl-array-bounds-01.shader_test b/tests/shaders/glsl-array-bounds-01.shader_test
> index 2e7c762..a06fef7 100644
> --- a/tests/shaders/glsl-array-bounds-01.shader_test
> +++ b/tests/shaders/glsl-array-bounds-01.shader_test
> @@ -15,21 +15,21 @@ void main()
>   */
>  #version 120
>
>  float array[] = float [] (1.0, 2.0, 3.0, 4.0);
>
>  void main()
>  {
>     int idx = 20;
>
>     if (array[idx] == 5.0)
> -      gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
> +      gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
>     else
>        gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
>  }

I'm a bit concerned that an optimizer will do tail-merging followed by 
eliminating the load. Maybe do something silly like

float tmp = array[idx];

gl_FragColor = vec4(0.0, 1.0 + abs(tmp), 0.0, 1.0);

instead? Then the compiler can't optimize the load away, because the 
shader has to work with un-clamped floating point framebuffers.

On second thought, what about NaNs?

Cheers,
Nicolai

>
>  [test]
>  clear color 0.0 0.0 0.0 0.0
>  clear
>  ortho
>  draw rect 10 10 10 10
>  probe rgb 15 15 0.0 1.0 0.0
>


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