[Piglit] [PATCH 3/3] arb_gpu_shader5: interpolateAt* must reject inputs in structs

[Nicolai Hähnle]

On 19.06.2017 23:46, Ian Romanick wrote:
> That's actually a little surprising... do other drivers reject this?  If
> so, I'll agree with Timothy that a spec quote would be nice.

So, I guess I was going off of what was in the Mesa source already, plus 
the spec part of Section 8.13.2 (Interpolation Functions) of GLSL 4.50 
which says:

    "For all of the interpolation functions, interpolant must be an
     input variable or an element of an input variable declared as an
     array. Component selection operators (e.g., .xy) may be used when
     specifying interpolant."

... and if you go out of your way to explicitly say that it *can* be an 
element of an array, one kind of expects that it *cannot* be an element 
of a struct. But maybe that's an artifact of how the spec evolved? 
Actually, now that I re-read it, our rejection of swizzles also looks 
incorrect.

As for compilers I can test:

glslangValidator: accepts swizzles and struct elements
amdgpu-pro: accepts struct elements but rejects swizzles; it does accept 
non-swizzling individual component selection, which seems like a spec 
misunderstanding given how "component selection" is defined in Section 
5.5 (Vector and Scalar Components and Length).
Mesa: rejects swizzles and struct elements

Going back to the ARB_gpu_shader5 spec, it explicitly forbids swizzles 
(there's an additional "not" in the sentence quoted above). So that 
seems to have changed at some point and we simply missed it. More 
digging needed...

Honestly, I'd interpret the spec language above in a way that forbids 
using struct elements. The other compilers I can test disagree, but both 
of them aren't exactly known for their high quality...

Cheers,
Nicolai

> 
> On 06/16/2017 01:34 PM, Nicolai Hähnle wrote:
>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>
>> ---
>>   .../fs-interpolateAtCentroid-struct.frag                | 17 +++++++++++++++++
>>   .../fs-interpolateAtOffset-struct.frag                  | 17 +++++++++++++++++
>>   .../fs-interpolateAtSampler-struct.frag                 | 17 +++++++++++++++++
>>   3 files changed, 51 insertions(+)
>>   create mode 100644 tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtCentroid-struct.frag
>>   create mode 100644 tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtOffset-struct.frag
>>   create mode 100644 tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtSampler-struct.frag
>>
>> diff --git a/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtCentroid-struct.frag b/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtCentroid-struct.frag
>> new file mode 100644
>> index 0000000..453c2db
>> --- /dev/null
>> +++ b/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtCentroid-struct.frag
>> @@ -0,0 +1,17 @@
>> +// [config]
>> +// expect_result: fail
>> +// glsl_version: 1.50
>> +// require_extensions: GL_ARB_gpu_shader5
>> +// [end config]
>> +
>> +#version 150
>> +#extension GL_ARB_gpu_shader5: require
>> +
>> +in struct {
>> +   vec4 a;
>> +} a;
>> +
>> +void main()
>> +{
>> +   interpolateAtCentroid(a.a);
>> +}
>> diff --git a/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtOffset-struct.frag b/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtOffset-struct.frag
>> new file mode 100644
>> index 0000000..9b7ee7e
>> --- /dev/null
>> +++ b/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtOffset-struct.frag
>> @@ -0,0 +1,17 @@
>> +// [config]
>> +// expect_result: fail
>> +// glsl_version: 1.50
>> +// require_extensions: GL_ARB_gpu_shader5
>> +// [end config]
>> +
>> +#version 150
>> +#extension GL_ARB_gpu_shader5: require
>> +
>> +in struct {
>> +   vec4 a;
>> +} a;
>> +
>> +void main()
>> +{
>> +   interpolateAtOffset(a.a, vec2(0));
>> +}
>> diff --git a/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtSampler-struct.frag b/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtSampler-struct.frag
>> new file mode 100644
>> index 0000000..78a844e
>> --- /dev/null
>> +++ b/tests/spec/arb_gpu_shader5/compiler/builtin-functions/fs-interpolateAtSampler-struct.frag
>> @@ -0,0 +1,17 @@
>> +// [config]
>> +// expect_result: fail
>> +// glsl_version: 1.50
>> +// require_extensions: GL_ARB_gpu_shader5
>> +// [end config]
>> +
>> +#version 150
>> +#extension GL_ARB_gpu_shader5: require
>> +
>> +in struct {
>> +   vec4 a;
>> +} a;
>> +
>> +void main()
>> +{
>> +   interpolateAtSample(a.a, 0);
>> +}
>>
> 


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Aber vergiss niemals, wie sie sein sollte.