Validator disallows Float16 capability even when the necessary extension is present

[ehsannas]

I am trying to validate a SPIR-V file that includes usages of 16-bit float.

The validator complains that:

Capability Float16 is not allowed by Vulkan 1.0 specification (or requires extension)

However, my SPIR-V contains OpExtension "SPV_AMD_gpu_shader_half_float" which is the extension that enables this capability. Attached is the SPIR-V source.

float16.txt

[atgoo]

The validator simply ignores this extension since it's not in the grammar, so there are no rules for it.

I could hardcode this particular case somewhere, but I think it's more of a question for @dneto0.

[ehsannas]

It turns out that specifying the "SPV_AMD_gpu_shader_half_float" extension does not necessarily mean Float16 capability should be enabled. Nothing needs to be done. Sorry for the confusion.

[ehsannas]

Ok, so there is still some work that needs to be done.

If Float16 capability is not specified, you will get this error:

Using a 16-bit floating point type requires the Float16 or Float16Buffer capability, or an extension that explicitly enables 16-bit floating point.

But we should not get this validation error if the "SPV_AMD_gpu_shader_half_float" extension is specified.

[ehsannas]

conclusion of my talk with @dneto0 was that we should tell the validator about this extension and the fact that it enables 16bit floats by adding it to the Features in the validation state.

[oscarbg]

just let me join the discussion and say that it is strange as with SPIRV-tools from Vulkan SDK 1.0.68 all works OK (EDIT: I mean SPIR-V code with Float16 cap+ SPV_AMD_.. ext):

spirv-val --version
SPIRV-Tools v2018.1-dev v2018.0-6-g9e19fc0

spirv-val doesn't catch any issues with the generated SPIR-V with Float16 cap+ SPV_AMD_.. ext:
spirv-as test.spv.txt -o test.spv
I run spirv-dis just to check spirv-as has mantained Float16 and SPV_AMD_.. ext:
spirv-dis test.spv -o testdis.spv.txt
spirv-val test.spv
no errors and also
spirv-opt test.spv -O -o test2.spv
optimzes spir-v correctly seeing textual form:
spirv-dis test2.spv -o test2dis.spv.txt
I attach all generated files in case helpful:

tests.zip