DX12 textureLoad from a Stencil8 value in GREEN channel instead of RED

[jbatez]

When I use WGSL textureLoad to read from a texture_2d<u32> bound to a Stencil8 texture view using the DX12 backend, the expected stencil value is in the GREEN channel. I expect it in the RED channel because of the WebGPU spec:

Reading or sampling the depth or stencil aspect of a texture behaves as if the texture contains the values (V, X, X, X), where V is the actual depth or stencil value, and each X is an implementation-defined unspecified value.

When I use the Vulkan backend instead, the value is in the RED channel as expected.

I assume this is because the actual SRV format the DX12 backend uses is DXGI_FORMAT_X24_TYPELESS_G8_UINT. I think you could use D3D12_SHADER_RESOURCE_VIEW_DESC::Shader4ComponentMapping to swizzle it into the RED channel.