[Piglit] [PATCH] Add glsl-array-bounds-13.shader_test tests

[Eric Anholt]

Nicolai Hähnle <nhaehnle at gmail.com> writes:

> On 11.08.2016 07:56, Tapani Pälli wrote:
>> Hi;
>>
>> On 08/10/2016 09:34 PM, Nicolai Hähnle wrote:
>>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>>
>>> Compared to the other array bounds tests, this one exercises a larger
>>> array
>>> size.
>>>
>>> The motivation is for Radeon, where arrays can be lowered either into the
>>> register file or into "real" memory. The larger array in this test
>>> will be
>>> sure to hit real memory.
>>> ---
>>>  tests/shaders/glsl-array-bounds-13.shader_test | 33
>>> ++++++++++++++++++++++++++
>>>  1 file changed, 33 insertions(+)
>>>  create mode 100644 tests/shaders/glsl-array-bounds-13.shader_test
>>>
>>> diff --git a/tests/shaders/glsl-array-bounds-13.shader_test
>>> b/tests/shaders/glsl-array-bounds-13.shader_test
>>> new file mode 100644
>>> index 0000000..95aa550
>>> --- /dev/null
>>> +++ b/tests/shaders/glsl-array-bounds-13.shader_test
>>> @@ -0,0 +1,33 @@
>>> +[require]
>>> +GLSL >= 1.20
>>> +
>>> +[vertex shader passthrough]
>>> +
>>> +[fragment shader]
>>> +/* Verify that out-of-bounds access to an array does not result in
>>> any sort of
>>> + * program interruption.
>>> + *
>>> + * This test case uses a larger array, to cover drivers that have
>>> different
>>> + * lowering paths for different array sizes.
>>> + *
>>> + * In this test case the array index will not be constant folded.
>>> + */
>>> +#version 120
>>> +
>>> +uniform int idx;
>>> +float array[32];
>>> +
>>> +void main()
>>> +{
>>> +   /* Ensure that there can be no constant folding due to undefined
>>> values. */
>>> +   array[0] = 0.0;
>>> +   array[1] = 1.0;
>>> +   gl_FragColor = vec4(0.0, 1.0, 0.0, array[idx]);
>>> +}
>>> +
>>> +[test]
>>> +uniform int idx -2
>>
>> According to GLSL 1.20 specs (and up to 4.50 spec):
>>
>> 'Undefined behavior results from indexing an array with a non-constant
>> expression that’s greater than or equal to the array’s size or less than
>> 0."
>>
>> Having said that, we seem to have many similar tests so I guess it's
>> fine to assume some output from the shader, just wanted to prompt that
>> perhaps we are testing something that is undefined here?
>
> I think you're right in theory. Undefined behavior might mean that the 
> pixel shader gets terminated without writing anything to the 
> framebuffer, though it definitely isn't allowed to mean program 
> termination or hangs.
>
> In practice, given that nobody has complained about these tests in the 
> past, the UB seems to be limited to undefined data results in all 
> implementations... if anybody ever complains, we might have to remove 
> the probe checks from the test script.

I've definitely had to remove people's broken probes for undefined array
accesses in the past.  Please remove the probe checks now.
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