register usage incorrectly produces a warning and suggests [[vk::binding(...)]]

[stanoddly]

If I try to compile this shader:

Sampler2D CombinedSampler : register(t0): register(s0);

[shader("fragment")]
float4 main(float2 TexCoord : TEXCOORD0) : SV_Target0
{
    return CombinedSampler.Sample(TexCoord);
}

via command line:

/opt/slang/bin/slangc shader.slang -target "spirv" -o "shader.spv"

it seems to generate shader.spv as expected, but also a warning is produced:

 warning 39013: shader parameter 'CombinedSampler' has a 'register' specified for D3D, but no '[[vk::binding(...)]]` specified for Vulkan

However, such usage is explicitly documented in "SPIR-V specific functionalities" (link):

Combined texture sampler

Slang supports Combined texture sampler such as Sampler2D. Slang emits SPIR-V code with OpTypeSampledImage instruction.

You can specify two different register numbers for each: one for the texture register and another for the sampler register.

Sampler2D explicitBindingSampler : register(t4): register(s3);

So, there should be no warning for a register usage, shouldn't be? I know the warning could be disabled via -warnings-disable, however I would expect there is nothing to warn about or alternatively register usage shouldn't be documented.

I would personally say that any usage of register shouldn't produce any warning. I think the behavior should be aligned with how dxc - dxc produces no warnings when compiling to SPIR-V (source + verified manually).

[csyonghe]

We should remove this warning now that we now support the same -fvk-shift options as in DXC.