[Piglit] [PATCH 1/5] glsl-1.30: Test large local array

[Alejandro Piñeiro]

On 07/03/17 00:11, Glenn Kennard wrote:
> GPUs typically will need to spill/reload values
> for a large enough locally declared array.
> ---
>  .../execution/fs-large-local-array.shader_test     | 43 ++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
>  create mode 100644 tests/spec/glsl-1.30/execution/fs-large-local-array.shader_test
>
> diff --git a/tests/spec/glsl-1.30/execution/fs-large-local-array.shader_test b/tests/spec/glsl-1.30/execution/fs-large-local-array.shader_test
> new file mode 100644
> index 0000000..c050ba2
> --- /dev/null
> +++ b/tests/spec/glsl-1.30/execution/fs-large-local-array.shader_test
> @@ -0,0 +1,43 @@
> +# Test correct handling of local-scope declared arrays large enough to
> +# typically not fit into first level GPU memory such as its register file,
> +# requiring storing/loading to some device-specific scratch space.
> +#
> +# One hardware example is R600 where arrays larger than 124*vec4 cannot
> +# fit into its GPR register file and has to be spilled to scratch memory.
> +# As of 2017-03-06 this is the largest known register file of any GPU, so
> +# the test uses that as a size to guarantee some form of spilling on any GPU.
> +#
> +# GLSL 1.10 specification loosely implies a minimum limit of 64k elements
> +# for an array due to 16 bit minimum precision for integer indexes. This
> +# is higher than R600 scratch supports and likely more than many other gpus
> +# support in practice, so this test restricts itself to testing "large enough"
> +# array size.
> +#
> +# Later specifications leave this undefined but allow 32 bit integers for indexing.
> +[require]
> +GLSL >= 1.30
> +
> +[vertex shader passthrough]
> +
> +[fragment shader]
> +uniform uint i;
> +void main()
> +{
> +	uint A[130];
> +	A[20] = 0u;
> +	A[i] = 37u;
> +	gl_FragColor.rba = vec3(0.0, 0.0, 1.0);
> +	gl_FragColor.g = float(A[20] == 37u);

What's the idea behind this comparison? I guess that at some point of
your development, when it was not supported, A[20] or A[i] was not
properly assigned, or the comparison was not working properly. But it is
somewhat non-intuitive, at least to me.

> +}
> +
> +[test]
> +clear color 1.0 0.0 0.0 1.0
> +clear
> +uniform uint i 19
> +draw rect -1 -1 2 2
> +probe all rgba 0.0 0.0 0.0 1.0
> +
> +clear
> +uniform uint i 20
> +draw rect -1 -1 2 2
> +probe all rgba 0.0 1.0 0.0 1.0