#ifndef OPTHELPERS_H
#define OPTHELPERS_H

#ifdef __has_builtin
#define HAS_BUILTIN __has_builtin
#else
#define HAS_BUILTIN(x) (0)
#endif

#if defined(__GNUC__) || HAS_BUILTIN(__builtin_expect)
/* LIKELY optimizes the case where the condition is true. The condition is not
 * required to be true, but it can result in more optimal code for the true
 * path at the expense of a less optimal false path.
 */
#define LIKELY(x) (__builtin_expect(!!(x), !false))
constexpr bool likely(bool expr) { return __builtin_expect(expr, true); }
/* The opposite of LIKELY, optimizing the case where the condition is false. */
#define UNLIKELY(x) (__builtin_expect(!!(x), false))
constexpr bool unlikely(bool expr) { return __builtin_expect(expr, false); }

#else

#define LIKELY(x) (!!(x))
#define UNLIKELY(x) (!!(x))
constexpr bool likely(bool expr) { return expr; }
constexpr bool unlikely(bool expr) { return expr; }
#endif

#if HAS_BUILTIN(__builtin_assume)
/* Unlike LIKELY, ASSUME requires the condition to be true or else it invokes
 * undefined behavior. It's essentially an assert without actually checking the
 * condition at run-time, allowing for stronger optimizations than LIKELY.
 */
#define ASSUME __builtin_assume
#elif defined(_MSC_VER)
#define ASSUME __assume
#elif defined(__GNUC__)
#define ASSUME(x) do { if(!(x)) __builtin_unreachable(); } while(0)
#else
#define ASSUME(x) ((void)0)
#endif

#if __cplusplus >= 201703L || defined(__cpp_if_constexpr)
#define if_constexpr if constexpr
#else
#define if_constexpr if
#endif

#endif /* OPTHELPERS_H */