mirror of
https://github.com/love2d/megasource.git
synced 2026-08-17 19:24:09 +02:00
Alex Szpakowski
88 lines
2.5 KiB
C++
88 lines
2.5 KiB
C++
#ifndef OPTHELPERS_H
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#define OPTHELPERS_H
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#include <cstdint>
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#include <utility>
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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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#ifdef __GNUC__
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#define force_inline [[gnu::always_inline]]
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#elif defined(_MSC_VER)
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#define force_inline __forceinline
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#else
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#define force_inline inline
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#endif
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#if defined(__GNUC__) || HAS_BUILTIN(__builtin_expect)
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/* likely() optimizes for the case where the condition is true. The condition
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* is not required to be true, but it can result in more optimal code for the
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* true path at the expense of a less optimal false path.
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*/
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template<typename T>
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force_inline constexpr bool likely(T&& expr) noexcept
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{ return __builtin_expect(static_cast<bool>(std::forward<T>(expr)), true); }
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/* The opposite of likely(), optimizing for the case where the condition is
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* false.
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*/
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template<typename T>
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force_inline constexpr bool unlikely(T&& expr) noexcept
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{ return __builtin_expect(static_cast<bool>(std::forward<T>(expr)), false); }
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#else
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template<typename T>
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force_inline constexpr bool likely(T&& expr) noexcept
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{ return static_cast<bool>(std::forward<T>(expr)); }
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template<typename T>
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force_inline constexpr bool unlikely(T&& expr) noexcept
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{ return static_cast<bool>(std::forward<T>(expr)); }
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#endif
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#define LIKELY(x) (likely(x))
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#define UNLIKELY(x) (unlikely(x))
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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) break; __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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namespace al {
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template<std::size_t alignment, typename T>
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force_inline constexpr auto assume_aligned(T *ptr) noexcept
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{
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#ifdef __cpp_lib_assume_aligned
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return std::assume_aligned<alignment,T>(ptr);
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#elif defined(__clang__) || (defined(__GNUC__) && !defined(__ICC))
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return static_cast<T*>(__builtin_assume_aligned(ptr, alignment));
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#elif defined(_MSC_VER)
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constexpr std::size_t alignment_mask{(1<<alignment) - 1};
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if((reinterpret_cast<std::uintptr_t>(ptr)&alignment_mask) == 0)
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return ptr;
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__assume(0);
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#elif defined(__ICC)
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__assume_aligned(ptr, alignment);
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return ptr;
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#else
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return ptr;
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#endif
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}
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} // namespace al
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#endif /* OPTHELPERS_H */
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