Chris Robinson
40 lines
1.1 KiB
C
40 lines
1.1 KiB
C
#ifndef OPTHELPERS_H
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#define OPTHELPERS_H
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#ifdef __has_builtin
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#define HAS_BUILTIN __has_builtin
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#else
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#define HAS_BUILTIN(x) (0)
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#endif
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#if defined(__GNUC__) || HAS_BUILTIN(__builtin_expect)
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/* LIKELY optimizes the case where the condition is true. The condition is not
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* required to be true, but it can result in more optimal code for the true
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* path at the expense of a less optimal false path.
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*/
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#define LIKELY(x) (__builtin_expect(!!(x), !false))
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/* The opposite of LIKELY, optimizing the case where the condition is false. */
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#define UNLIKELY(x) (__builtin_expect(!!(x), false))
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#else
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#define LIKELY(x) (!!(x))
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#define UNLIKELY(x) (!!(x))
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#endif
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#if HAS_BUILTIN(__builtin_assume)
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/* Unlike LIKELY, ASSUME requires the condition to be true or else it invokes
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* undefined behavior. It's essentially an assert without actually checking the
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* condition at run-time, allowing for stronger optimizations than LIKELY.
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*/
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#define ASSUME __builtin_assume
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#elif defined(_MSC_VER)
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#define ASSUME __assume
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#elif defined(__GNUC__)
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#define ASSUME(x) do { if(!(x)) __builtin_unreachable(); } while(0)
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#else
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#define ASSUME(x) ((void)0)
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#endif
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#endif /* OPTHELPERS_H */
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