| //===------------------------ memory.cpp ----------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "memory" |
| #ifndef _LIBCPP_HAS_NO_THREADS |
| #include "mutex" |
| #include "thread" |
| #if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB) |
| #pragma comment(lib, "pthread") |
| #endif |
| #endif |
| #include "include/atomic_support.h" |
| |
| _LIBCPP_BEGIN_NAMESPACE_STD |
| |
| const allocator_arg_t allocator_arg = allocator_arg_t(); |
| |
| bad_weak_ptr::~bad_weak_ptr() _NOEXCEPT {} |
| |
| const char* |
| bad_weak_ptr::what() const _NOEXCEPT |
| { |
| return "bad_weak_ptr"; |
| } |
| |
| __shared_count::~__shared_count() |
| { |
| } |
| |
| __shared_weak_count::~__shared_weak_count() |
| { |
| } |
| |
| #if defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS) |
| void |
| __shared_count::__add_shared() _NOEXCEPT |
| { |
| __libcpp_atomic_refcount_increment(__shared_owners_); |
| } |
| |
| bool |
| __shared_count::__release_shared() _NOEXCEPT |
| { |
| if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1) |
| { |
| __on_zero_shared(); |
| return true; |
| } |
| return false; |
| } |
| |
| void |
| __shared_weak_count::__add_shared() _NOEXCEPT |
| { |
| __shared_count::__add_shared(); |
| } |
| |
| void |
| __shared_weak_count::__add_weak() _NOEXCEPT |
| { |
| __libcpp_atomic_refcount_increment(__shared_weak_owners_); |
| } |
| |
| void |
| __shared_weak_count::__release_shared() _NOEXCEPT |
| { |
| if (__shared_count::__release_shared()) |
| __release_weak(); |
| } |
| |
| #endif // _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS |
| |
| void |
| __shared_weak_count::__release_weak() _NOEXCEPT |
| { |
| // NOTE: The acquire load here is an optimization of the very |
| // common case where a shared pointer is being destructed while |
| // having no other contended references. |
| // |
| // BENEFIT: We avoid expensive atomic stores like XADD and STREX |
| // in a common case. Those instructions are slow and do nasty |
| // things to caches. |
| // |
| // IS THIS SAFE? Yes. During weak destruction, if we see that we |
| // are the last reference, we know that no-one else is accessing |
| // us. If someone were accessing us, then they would be doing so |
| // while the last shared / weak_ptr was being destructed, and |
| // that's undefined anyway. |
| // |
| // If we see anything other than a 0, then we have possible |
| // contention, and need to use an atomicrmw primitive. |
| // The same arguments don't apply for increment, where it is legal |
| // (though inadvisable) to share shared_ptr references between |
| // threads, and have them all get copied at once. The argument |
| // also doesn't apply for __release_shared, because an outstanding |
| // weak_ptr::lock() could read / modify the shared count. |
| if (__libcpp_atomic_load(&__shared_weak_owners_, _AO_Acquire) == 0) |
| { |
| // no need to do this store, because we are about |
| // to destroy everything. |
| //__libcpp_atomic_store(&__shared_weak_owners_, -1, _AO_Release); |
| __on_zero_shared_weak(); |
| } |
| else if (__libcpp_atomic_refcount_decrement(__shared_weak_owners_) == -1) |
| __on_zero_shared_weak(); |
| } |
| |
| __shared_weak_count* |
| __shared_weak_count::lock() _NOEXCEPT |
| { |
| long object_owners = __libcpp_atomic_load(&__shared_owners_); |
| while (object_owners != -1) |
| { |
| if (__libcpp_atomic_compare_exchange(&__shared_owners_, |
| &object_owners, |
| object_owners+1)) |
| return this; |
| } |
| return nullptr; |
| } |
| |
| const void* |
| __shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT |
| { |
| return nullptr; |
| } |
| |
| #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER) |
| |
| _LIBCPP_SAFE_STATIC static const std::size_t __sp_mut_count = 16; |
| _LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut_back[__sp_mut_count] = |
| { |
| _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, |
| _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, |
| _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, |
| _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER |
| }; |
| |
| _LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT |
| : __lx(p) |
| { |
| } |
| |
| void |
| __sp_mut::lock() _NOEXCEPT |
| { |
| auto m = static_cast<__libcpp_mutex_t*>(__lx); |
| unsigned count = 0; |
| while (!__libcpp_mutex_trylock(m)) |
| { |
| if (++count > 16) |
| { |
| __libcpp_mutex_lock(m); |
| break; |
| } |
| this_thread::yield(); |
| } |
| } |
| |
| void |
| __sp_mut::unlock() _NOEXCEPT |
| { |
| __libcpp_mutex_unlock(static_cast<__libcpp_mutex_t*>(__lx)); |
| } |
| |
| __sp_mut& |
| __get_sp_mut(const void* p) |
| { |
| static __sp_mut muts[__sp_mut_count] |
| { |
| &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3], |
| &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7], |
| &mut_back[ 8], &mut_back[ 9], &mut_back[10], &mut_back[11], |
| &mut_back[12], &mut_back[13], &mut_back[14], &mut_back[15] |
| }; |
| return muts[hash<const void*>()(p) & (__sp_mut_count-1)]; |
| } |
| |
| #endif // !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER) |
| |
| void |
| declare_reachable(void*) |
| { |
| } |
| |
| void |
| declare_no_pointers(char*, size_t) |
| { |
| } |
| |
| void |
| undeclare_no_pointers(char*, size_t) |
| { |
| } |
| |
| #if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE) |
| pointer_safety get_pointer_safety() _NOEXCEPT |
| { |
| return pointer_safety::relaxed; |
| } |
| #endif |
| |
| void* |
| __undeclare_reachable(void* p) |
| { |
| return p; |
| } |
| |
| void* |
| align(size_t alignment, size_t size, void*& ptr, size_t& space) |
| { |
| void* r = nullptr; |
| if (size <= space) |
| { |
| char* p1 = static_cast<char*>(ptr); |
| char* p2 = reinterpret_cast<char*>(reinterpret_cast<size_t>(p1 + (alignment - 1)) & -alignment); |
| size_t d = static_cast<size_t>(p2 - p1); |
| if (d <= space - size) |
| { |
| r = p2; |
| ptr = r; |
| space -= d; |
| } |
| } |
| return r; |
| } |
| |
| _LIBCPP_END_NAMESPACE_STD |