On Wed, Oct 16, 2013 at 10:40 AM, Ian Romanick <i...@freedesktop.org> wrote:
> On 10/15/2013 07:50 PM, Kenneth Graunke wrote:
>> On 10/15/2013 01:58 PM, Ian Romanick wrote:
>>> On 10/15/2013 01:50 PM, Anuj Phogat wrote:
>>>> On Tue, Oct 15, 2013 at 10:02 AM, Ian Romanick <i...@freedesktop.org>
>>>> wrote:
>>>>> On 10/14/2013 10:12 AM, Anuj Phogat wrote:
>>>>>> @@ -789,6 +794,12 @@
>>>>>> builtin_variable_generator::generate_fs_special_vars()
>>>>>> if (state->AMD_shader_stencil_export_warn)
>>>>>> var->warn_extension = "GL_AMD_shader_stencil_export";
>>>>>> }
>>>>>> +
>>>>>> + if (state->ARB_sample_shading_enable) {
>>>>>> + add_input(VARYING_SLOT_SAMPLE_ID, int_t, "gl_SampleID");
>>>>>> + add_input(VARYING_SLOT_SAMPLE_POS, vec2_t, "gl_SamplePosition");
>>>>>> + add_output(FRAG_RESULT_SAMPLE_MASK, array(int_t, 1),
>>>>>> "gl_SampleMask");
>>>>>
>>>>> I don't see code anywhere in this patch series that correctly sizes this
>>>>> array. I thought gl_SampleMask.length() == gl_NumSamples... except you
>>>>> can't use .length() on gl_SampleMask because the size can't be known at
>>>>> compile-time. We should have a test that 'gl_SampleMask.length()' fails
>>>>> to compile. :)
>>>>>
>>>> I'll add a piglit compiler test for that.
>>>>
>>>>> The only other array that works like this is gl_TexCoord. That array is
>>>>> sized to 0 (line 837 of builtin_variables.cpp). I believe gl_SampleMask
>>>>> should do the same.
>>>>>
>>>> Yes, I noticed gl_TexCoord is using array size of 0 and it works for
>>>> gl_SampleMask as well. But, It generates same glsl ir with array size
>>>> of 0 or 1:
>>>> (declare (shader_out ) (array int 1) gl_SampleMask)
>>>>
>>>> what's the utility of using size 0?
>>>> I'll take care of rest of your comments in this patch.
>>>
>>> Using size 0 is like writing
>>>
>>> int gl_SampleMask[]; // unsized
>>>
>>> in the shader. Later during compilation, usually in linking, unsized
>>> arrays become sized. Somewhere between generating the built-in variable
>>> and printing the IR a size is established for it.
>>
>> Right, but gl_SampleMask is not an unsized array. It's statically sized
>> based on your implementation's maximum supported number of color samples
>> (ceil(samples/32)), and this is totally known at compile time...
>
> That doesn't match what the spec says. At least the GLSL 4.00 spec:
>
> "In the fragment language, built-in variables are intrinsically
> declared as:
>
> in vec4 gl_FragCoord;
> in bool gl_FrontFacing;
> in float gl_ClipDistance[];
> in vec2 gl_PointCoord;
> in int gl_PrimitiveID;
> in int gl_SampleID;
> in vec2 gl_SamplePosition;
> out vec4 gl_FragColor;
> out vec4 gl_FragData[gl_MaxDrawBuffers];
> out float gl_FragDepth;
> out int gl_SampleMask[];"
>
> Note that both gl_ClipDistance and gl_SampleMask are unsized, and both
> have a maximum size based on implementation limits. Later the GLSL 4.00
> spec says:
>
> "This array must be sized in the fragment shader either implicitly
> or explicitly to be the same size as the implementation-dependent
> maximum sample-mask (as an array of 32bit elements), determined by
> the maximum number of samples."
>
> The maximum size of the array is ceil(max_samples/32), but initially it
> is unsized.
To confirm, gl_NumSamples is the current number of samples we're
operating on, whereas gl_SampleMask[] is sized by the maximum number
of samples supported -- and therefore we can't use gl_NumSamples to
size gl_SampleMask[] in general.
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