[pixel shader todo]
float myfunc()
{
    return 0.6;
}
static float a = myfunc() + 0.2;
static float b;
static const float c;
float4 main() : sv_target
{
    return float4(a, b, c, 0);
}

[test]
todo draw quad
probe all rgba (0.8, 0.0, 0.0, 0.0)