mirror of
https://github.com/love2d/megasource.git
synced 2026-08-19 12:14:41 +02:00
Sasha Szpakowski
121 lines
3.3 KiB
C++
121 lines
3.3 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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#include <memory>
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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 __has_cpp_attribute
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#define HAS_ATTRIBUTE __has_cpp_attribute
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#else
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#define HAS_ATTRIBUTE(x) (0)
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#endif
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#ifdef __GNUC__
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#define force_inline [[gnu::always_inline]] inline
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#define NOINLINE [[gnu::noinline]]
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#elif defined(_MSC_VER)
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#define force_inline __forceinline
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#define NOINLINE __declspec(noinline)
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#else
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#define force_inline inline
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#define NOINLINE
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#endif
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#if defined(__MINGW32__) && defined(__i386__)
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/* 32-bit MinGW targets have a bug where __STDCPP_DEFAULT_NEW_ALIGNMENT__
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* reports 16, despite the default operator new calling standard malloc which
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* only guarantees 8-byte alignment. As a result, structs that need and specify
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* 16-byte alignment only get 8-byte alignment. Explicitly specifying 32-byte
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* alignment forces the over-aligned operator new to be called, giving the
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* correct (if larger than necessary) alignment.
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*
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* Technically this bug affects 32-bit GCC more generally, but typically only
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* with fairly old glibc versions as newer versions do guarantee the 16-byte
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* alignment as specified. MinGW is reliant on msvcrt.dll's malloc however,
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* which can't be updated to give that guarantee.
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*/
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#define SIMDALIGN alignas(32)
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#else
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#define SIMDALIGN
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#endif
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/* Unlike the likely attribute, ASSUME requires the condition to be true or
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* else it invokes undefined behavior. It's essentially an assert without
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* actually checking the condition at run-time, allowing for stronger
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* optimizations than the likely attribute.
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*/
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#if HAS_BUILTIN(__builtin_assume)
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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 __has_attribute(assume)
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#define ASSUME(x) [[assume(x)]]
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#elif HAS_BUILTIN(__builtin_unreachable)
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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) (static_cast<void>(0))
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#endif
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/* This shouldn't be needed since unknown attributes are ignored, but older
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* versions of GCC choke on the attribute syntax in certain situations.
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*/
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#if HAS_ATTRIBUTE(likely)
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#define LIKELY [[likely]]
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#define UNLIKELY [[unlikely]]
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#else
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#define LIKELY
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#define UNLIKELY
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#endif
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#if !defined(_WIN32) && HAS_ATTRIBUTE(gnu::visibility)
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#define DECL_HIDDEN [[gnu::visibility("hidden")]]
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#else
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#define DECL_HIDDEN
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#endif
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namespace al {
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template<typename T>
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constexpr std::underlying_type_t<T> to_underlying(T e) noexcept
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{ return static_cast<std::underlying_type_t<T>>(e); }
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[[noreturn]] inline void unreachable()
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{
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#if HAS_BUILTIN(__builtin_unreachable)
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__builtin_unreachable();
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#else
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ASSUME(false);
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#endif
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}
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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 HAS_BUILTIN(__builtin_assume_aligned)
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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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