How to mark a condition is likeyly or unlikey ？

[lili]

Hi：
     In C there has likely unlikely marco used by condition 
expression。
     #define likely(x) __builtin_expect(!!(x), 1)
     #define unlikely(x) __builtin_expect(!!(x), 0)
     if (likely(var > 1)) do...

     How to do this in Dlang？