Missing SM 6.6 function: IsHelperLane()

[chaoticbob]

Compiling the shader below results in this error message:

shader.hlsl(8): error 30015: undefined identifier 'IsHelperLane'.
    if (IsHelperLane()) ret = 2.0;
        ^~~~~~~~~~~~

CMD

slangc.exe -target spirv -lang slang -D__spirv__ -emit-spirv-directly -profile ps_6_6 -entry main

Would be useful to have this function to ease porting of advanced shaders.

Shader

float4 main() : SV_Target {
    float ret = 1.0;

    if (IsHelperLane()) ret = 2.0;

    return (float4)ret;
}

[jkwak-work]

This looks like a good first bug for @venkataram-nv .
I am assigning it to him.

[chaoticbob]

Just FYI...for both DXC emulates this function starting in SM 6.0 and before SM 6.6.