Compiling mesh shader(ms_6_5) with SV_ShadingRate produces error: Semantic SV_ShadingRate is invalid for shader model: ms

[AnimeIncarnation]

According to https://microsoft.github.io/DirectX-Specs/d3d/VariableRateShading.html, the description of VariableRateShading.

Per perimitive sementic SV_ShadingRate is supported in ShaderModel 6.4, and my graphics hardware support the "MeshShaderPerPrimitiveShadingRateSupported" graphics tier in DirectX12 API.

So I'm looking forward to use VRS in mesh shader. But when I try to compile my mesh shader, the error tells me that SV_ShadeingRate is invalid for ms_6_5.

I'm not sure whether this is a bug or it's just DXC compiler don't support mesh shader VRS. I've tried SV_ShadingRate in a vertex shader and DXC compiled it successfully.

Steps to Reproduce (if applicable)

1. Write a mesh shader with SV_ShadingRate
2. Command line arguments : dxc -E main -T ms_6_5 -Fo "MeshShader.cso" -Od -Zi "MeshShader.hlsl"
3. Error report: Semantic SV_ShadingRate is invalid for shader model: ms

Environment

• DXC version dxcompiler.dll: 1.8 - 1.8.2407.7 (416fab6b5); dxil.dll: 1.8(101.8.2407.12)
• Host Operating System : win10 19045.5247

[damyanp]

Moved this to hlsl-specs: even if this wasn't intentional, there can't be anything validating that drivers support this, so addressing this would be a new shader model feature.