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#ifndef OPTHELPERS_H
#define OPTHELPERS_H
#include <cstdint>
#include <utility>
#include <memory>
#ifdef __has_builtin
#define HAS_BUILTIN __has_builtin
#else
#define HAS_BUILTIN(x) (0)
#endif
#ifdef __has_cpp_attribute
#define HAS_ATTRIBUTE __has_cpp_attribute
#else
#define HAS_ATTRIBUTE(x) (0)
#endif
#ifdef __GNUC__
#define force_inline [[gnu::always_inline]] inline
#elif defined(_MSC_VER)
#define force_inline __forceinline
#else
#define force_inline inline
#endif
/* Unlike the likely attribute, 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 the likely attribute.
*/
#if HAS_BUILTIN(__builtin_assume)
#define ASSUME __builtin_assume
#elif defined(_MSC_VER)
#define ASSUME __assume
#elif __has_attribute(assume)
#define ASSUME(x) [[assume(x)]]
#elif HAS_BUILTIN(__builtin_unreachable)
#define ASSUME(x) do { if(x) break; __builtin_unreachable(); } while(0)
#else
#define ASSUME(x) ((void)0)
#endif
/* This shouldn't be needed since unknown attributes are ignored, but older
* versions of GCC choke on the attribute syntax in certain situations.
*/
#if HAS_ATTRIBUTE(likely)
#define LIKELY [[likely]]
#define UNLIKELY [[unlikely]]
#else
#define LIKELY
#define UNLIKELY
#endif
namespace al {
template<typename T>
constexpr std::underlying_type_t<T> to_underlying(T e) noexcept
{ return static_cast<std::underlying_type_t<T>>(e); }
[[noreturn]] inline void unreachable()
{
#if HAS_BUILTIN(__builtin_unreachable)
__builtin_unreachable();
#else
ASSUME(false);
#endif
}
template<std::size_t alignment, typename T>
force_inline constexpr auto assume_aligned(T *ptr) noexcept
{
#ifdef __cpp_lib_assume_aligned
return std::assume_aligned<alignment,T>(ptr);
#elif HAS_BUILTIN(__builtin_assume_aligned)
return static_cast<T*>(__builtin_assume_aligned(ptr, alignment));
#elif defined(_MSC_VER)
constexpr std::size_t alignment_mask{(1<<alignment) - 1};
if((reinterpret_cast<std::uintptr_t>(ptr)&alignment_mask) == 0)
return ptr;
__assume(0);
#elif defined(__ICC)
__assume_aligned(ptr, alignment);
return ptr;
#else
return ptr;
#endif
}
} // namespace al
#endif /* OPTHELPERS_H */
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