likely/unlikely equivalent for MSVC

Question

GCC compiler supports __builtin_expect statement that is used to define likely and unlikely macros.

eg.

#define likely(expr)    __builtin_expect((expr), !0)
#define unlikely(expr)  __builtin_expect((expr), 0)

Is there an equivalent statement for the Microsoft Visual C compiler, or something equivalent ?

Answer 1

__assume should be similar.

However, if you want to do this really well you should use Profile Guided Optimization rather than static hints.

Answer 2

I say just punt

The only thing close is the semi-intrinsic __assume(), but don't use it, it is dangerous. You can get incorrect code generated if the expression turns out to be different.

Really, the reason the gnu builtin is wrapped in a macro is so you can just get rid of it automatically if __GNUC__ is not defined. There isn't anything the least bit necessary about those macros and I bet you will not notice the run time difference.

Summary

Just get rid of (null out) *likely on non-GNU. You won't miss it.