Problem with Slang layout in D3D12

[tdavidovicNV]

Compiling this small shader:

cbuffer vertexCB { uniform float4x4 matrix; }
cbuffer pixelCB { uniform Texture2D texture; }
uniform uint data[3];

struct VertexInputs { float3 p : POSITION; }

[shader("vertex")]
float4 vertexMain(VertexInputs vi) : SV_Position
{
    return mul(float4(vi.p, 1.0), matrix);
}

[shader("fragment")]
float4 fragmentMain(float4 SV_Position : SV_Position) : SV_Target
{
	return float4(SV_Position.xyz, 1.0);
}

Results in this error when creating pipeline for D3D12.

D3D12 ERROR: ID3D12Device::CreateGraphicsPipelineState: Root Signature doesn't match Vertex Shader: Shader CBV descriptor range (BaseShaderRegister=1, NumDescriptors=1, RegisterSpace=0) is not fully bound in root signature
 [ STATE_CREATION ERROR #688: CREATEGRAPHICSPIPELINESTATE_VS_ROOT_SIGNATURE_MISMATCH]

If the uniform uint data[3]; is not present at all, or is part of either of the two cbuffers, things work as you'd expect.
Also, if I comment out the indicated line in d3d12-shader-object-layout.cpp in:

void RootShaderObjectLayoutImpl::RootSignatureDescBuilder::addAsConstantBuffer(
    slang::TypeLayoutReflection* typeLayout,
    uint32_t physicalDescriptorSetIndex,
    BindingRegisterOffsetPair offsetForChildrenThatNeedNewSpace,
    BindingRegisterOffsetPair offsetForOrdinaryChildren
)
{
    if (typeLayout->getSize(SLANG_PARAMETER_CATEGORY_UNIFORM) != 0)
    {
        auto descriptorRangeType = D3D12_DESCRIPTOR_RANGE_TYPE_CBV;
        auto& offsetForRangeType = offsetForOrdinaryChildren.primary.offsetForRangeType[descriptorRangeType];
        addDescriptorRange(
            physicalDescriptorSetIndex,
            descriptorRangeType,
            offsetForRangeType,
            offsetForOrdinaryChildren.primary.spaceOffset,
            1,
            false
        );
        // offsetForRangeType++; // <-- This line
    }

    addAsValue(typeLayout, physicalDescriptorSetIndex, offsetForChildrenThatNeedNewSpace, offsetForOrdinaryChildren);
}

Things work (and no other test seems to break). But I cannot propose this change as a fix, because I do not understand all the implications. So it can at best serve as an indication of where the problem lies.

[bmillsNV]

@tdavidovicNV is this issue blocking you?

[tdavidovicNV]

Absolutely not blocking me in any way, just filed it for reference.