glslang/Test/hlsl.nonint-index.frag

static const float array[3] = { 1, 2, 3 };

float main(float input : IN) : SV_Target0
{
    // non-integer indexes get converted to uints:
    //      uint(input)     3.0          2.0            1.0
    return array[input] + array[2.0] + array[true] + array[false];
}