diff options
Diffstat (limited to 'common')
| -rw-r--r-- | common/opthelpers.h | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/common/opthelpers.h b/common/opthelpers.h new file mode 100644 index 00000000..b496942c --- /dev/null +++ b/common/opthelpers.h @@ -0,0 +1,39 @@ +#ifndef OPTHELPERS_H +#define OPTHELPERS_H + +#ifdef __has_builtin +#define HAS_BUILTIN __has_builtin +#else +#define HAS_BUILTIN(x) (0) +#endif + +#ifdef __GNUC__ +/* 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), !0) +/* The opposite of LIKELY, optimizing the case where the condition is false. */ +#define UNLIKELY(x) __builtin_expect(!!(x), 0) +/* 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. + */ +#if HAS_BUILTIN(__builtin_assume) +#define ASSUME __builtin_assume +#else +#define ASSUME(x) do { if(!(x)) __builtin_unreachable(); } while(0) +#endif + +#else /* __GNUC__ */ + +#define LIKELY(x) (!!(x)) +#define UNLIKELY(x) (!!(x)) +#ifdef _MSC_VER +#define ASSUME __assume +#else +#define ASSUME(x) ((void)0) +#endif /* _MSC_VER */ +#endif /* __GNUC__ */ + +#endif /* OPTHELPERS_H */ |