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

[Timothy Arceri]

On 31/03/17 17:30, Nicolai Hähnle wrote:
> 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?

Well we are testing undefined behavior, the correct thing might be to 
just delete the test?



>
> 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
>>
>
>