I’m working on a textbook PBR shader implementation using Metal.
While porting existing GLSL code, my goal was to pass a 3×3 matrix calculated in the vertex shader to the fragment shader. Doing so seems to not be supported by Metal given the following compiler error message:

field of illegal type 'metal::float3x3' (aka 'matrix<float, 3, 3>')

Vertex shader code sample:

typedef struct
{
    float4 position [[position]];
    float3 worldPosition;
    float2 texCoord;
    float3x3 tangentBasis; // <-- field of illegal type 'metal::float3x3' (aka 'matrix<float, 3, 3>')
} ColorInOut;

vertex ColorInOut vertexShader(Vertex in [[stage_in]])
{
    ColorInOut out;
    // [...] omitted shader code for simplicity
    out.tangentBasis = float3x3(/* ... */);
    return out;
}

Is this an actual limitation in the Metal Shading Language? Do I need to explicitly deconstruct my matrix into 3 vectors?

Thank you!