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|
//===------------------------ 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
#if !defined(_LIBCPP_HAS_NO_THREADS)
#include <atomic>
#else
#include "include/atomic_support.h"
#endif
_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
{
#ifdef _LIBCPP_HAS_NO_THREADS
__libcpp_atomic_refcount_increment(__shared_owners_);
#else
++__shared_owners_;
#endif
}
bool
__shared_count::__release_shared() noexcept
{
#ifdef _LIBCPP_HAS_NO_THREADS
if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1)
#else
if (--__shared_owners_ == -1)
#endif
{
__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
{
#ifdef _LIBCPP_HAS_NO_THREADS
__libcpp_atomic_refcount_increment(__shared_weak_owners_);
#else
++__shared_weak_owners_;
#endif
}
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.
#ifdef _LIBCPP_HAS_NO_THREADS
if (__libcpp_atomic_load(&__shared_weak_owners_, _AO_Acquire) == 0)
#else
if (__shared_weak_owners_.load(memory_order_acquire) == 0)
#endif
{
// 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();
}
#ifdef _LIBCPP_HAS_NO_THREADS
else if (__libcpp_atomic_refcount_decrement(__shared_weak_owners_) == -1)
#else
else if (--__shared_weak_owners_ == -1)
#endif
__on_zero_shared_weak();
}
__shared_weak_count*
__shared_weak_count::lock() noexcept
{
#ifdef _LIBCPP_HAS_NO_THREADS
long object_owners = __libcpp_atomic_load(&__shared_owners_);
#else
long object_owners = __shared_owners_.load();
#endif
while (object_owners != -1)
{
#ifdef _LIBCPP_HAS_NO_THREADS
if (__libcpp_atomic_compare_exchange(&__shared_owners_,
&object_owners,
object_owners+1))
#else
if (__shared_owners_.compare_exchange_weak(object_owners, object_owners+1))
#endif
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)
{
}
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
|
