//===----------------------------------------------------------------------===//
//
// 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>
#include <memory_resource>
#ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
# include <atomic>
#elif !defined(_LIBCPP_HAS_NO_THREADS)
# include <mutex>
# if defined(__ELF__) && defined(_LIBCPP_LINK_PTHREAD_LIB)
# pragma comment(lib, "pthread")
# endif
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
namespace pmr {
// memory_resource
memory_resource::~memory_resource() = default;
// new_delete_resource()
#ifdef _LIBCPP_HAS_NO_ALIGNED_ALLOCATION
static bool is_aligned_to(void* ptr, size_t align) {
void* p2 = ptr;
size_t space = 1;
void* result = std::align(align, 1, p2, space);
return (result == ptr);
}
#endif
class _LIBCPP_EXPORTED_FROM_ABI __new_delete_memory_resource_imp : public memory_resource {
void* do_allocate(size_t bytes, size_t align) override {
#ifndef _LIBCPP_HAS_NO_ALIGNED_ALLOCATION
return std::__libcpp_allocate(bytes, align);
#else
if (bytes == 0)
bytes = 1;
void* result = std::__libcpp_allocate(bytes, align);
if (!is_aligned_to(result, align)) {
std::__libcpp_deallocate(result, bytes, align);
__throw_bad_alloc();
}
return result;
#endif
}
void do_deallocate(void* p, size_t bytes, size_t align) override { std::__libcpp_deallocate(p, bytes, align); }
bool do_is_equal(const memory_resource& other) const noexcept override { return &other == this; }
};
// null_memory_resource()
class _LIBCPP_EXPORTED_FROM_ABI __null_memory_resource_imp : public memory_resource {
void* do_allocate(size_t, size_t) override { __throw_bad_alloc(); }
void do_deallocate(void*, size_t, size_t) override {}
bool do_is_equal(const memory_resource& other) const noexcept override { return &other == this; }
};
namespace {
union ResourceInitHelper {
struct {
__new_delete_memory_resource_imp new_delete_res;
__null_memory_resource_imp null_res;
} resources;
char dummy;
constexpr ResourceInitHelper() : resources() {}
~ResourceInitHelper() {}
};
// Pretend we're inside a system header so the compiler doesn't flag the use of the init_priority
// attribute with a value that's reserved for the implementation (we're the implementation).
#include "memory_resource_init_helper.h"
} // namespace
memory_resource* new_delete_resource() noexcept { return &res_init.resources.new_delete_res; }
memory_resource* null_memory_resource() noexcept { return &res_init.resources.null_res; }
// default_memory_resource()
static memory_resource* __default_memory_resource(bool set = false, memory_resource* new_res = nullptr) noexcept {
#ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
static constinit atomic<memory_resource*> __res{&res_init.resources.new_delete_res};
if (set) {
new_res = new_res ? new_res : new_delete_resource();
// TODO: Can a weaker ordering be used?
return std::atomic_exchange_explicit(&__res, new_res, memory_order_acq_rel);
} else {
return std::atomic_load_explicit(&__res, memory_order_acquire);
}
#elif !defined(_LIBCPP_HAS_NO_THREADS)
static constinit memory_resource* res = &res_init.resources.new_delete_res;
static mutex res_lock;
if (set) {
new_res = new_res ? new_res : new_delete_resource();
lock_guard<mutex> guard(res_lock);
memory_resource* old_res = res;
res = new_res;
return old_res;
} else {
lock_guard<mutex> guard(res_lock);
return res;
}
#else
static constinit memory_resource* res = &res_init.resources.new_delete_res;
if (set) {
new_res = new_res ? new_res : new_delete_resource();
memory_resource* old_res = res;
res = new_res;
return old_res;
} else {
return res;
}
#endif
}
memory_resource* get_default_resource() noexcept { return __default_memory_resource(); }
memory_resource* set_default_resource(memory_resource* __new_res) noexcept {
return __default_memory_resource(true, __new_res);
}
// 23.12.5, mem.res.pool
static size_t roundup(size_t count, size_t alignment) {
size_t mask = alignment - 1;
return (count + mask) & ~mask;
}
struct unsynchronized_pool_resource::__adhoc_pool::__chunk_footer {
__chunk_footer* __next_;
char* __start_;
size_t __align_;
size_t __allocation_size() { return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this); }
};
void unsynchronized_pool_resource::__adhoc_pool::__release_ptr(memory_resource* upstream) {
while (__first_ != nullptr) {
__chunk_footer* next = __first_->__next_;
upstream->deallocate(__first_->__start_, __first_->__allocation_size(), __first_->__align_);
__first_ = next;
}
}
void* unsynchronized_pool_resource::__adhoc_pool::__do_allocate(memory_resource* upstream, size_t bytes, size_t align) {
const size_t footer_size = sizeof(__chunk_footer);
const size_t footer_align = alignof(__chunk_footer);
if (align < footer_align)
align = footer_align;
size_t aligned_capacity = roundup(bytes, footer_align) + footer_size;
void* result = upstream->allocate(aligned_capacity, align);
__chunk_footer* h = (__chunk_footer*)((char*)result + aligned_capacity - footer_size);
h->__next_ = __first_;
h->__start_ = (char*)result;
h->__align_ = align;
__first_ = h;
return result;
}
void unsynchronized_pool_resource::__adhoc_pool::__do_deallocate(
memory_resource* upstream, void* p, size_t bytes, size_t align) {
_LIBCPP_ASSERT_NON_NULL(__first_ != nullptr, "deallocating a block that was not allocated with this allocator");
if (__first_->__start_ == p) {
__chunk_footer* next = __first_->__next_;
upstream->deallocate(p, __first_->__allocation_size(), __first_->__align_);
__first_ = next;
} else {
for (__chunk_footer* h = __first_; h->__next_ != nullptr; h = h->__next_) {
if (h->__next_->__start_ == p) {
__chunk_footer* next = h->__next_->__next_;
upstream->deallocate(p, h->__next_->__allocation_size(), h->__next_->__align_);
h->__next_ = next;
return;
}
}
// The request to deallocate memory ends up being a no-op, likely resulting in a memory leak.
_LIBCPP_ASSERT_VALID_DEALLOCATION(false, "deallocating a block that was not allocated with this allocator");
}
}
class unsynchronized_pool_resource::__fixed_pool {
struct __chunk_footer {
__chunk_footer* __next_;
char* __start_;
size_t __align_;
size_t __allocation_size() { return (reinterpret_cast<char*>(this) - __start_) + sizeof(*this); }
};
struct __vacancy_header {
__vacancy_header* __next_vacancy_;
};
__chunk_footer* __first_chunk_ = nullptr;
__vacancy_header* __first_vacancy_ = nullptr;
public:
explicit __fixed_pool() = default;
void __release_ptr(memory_resource* upstream) {
__first_vacancy_ = nullptr;
while (__first_chunk_ != nullptr) {
__chunk_footer* next = __first_chunk_->__next_;
upstream->deallocate(__first_chunk_->__start_, __first_chunk_->__allocation_size(), __first_chunk_->__align_);
__first_chunk_ = next;
}
}
void* __try_allocate_from_vacancies() {
if (__first_vacancy_ != nullptr) {
void* result = __first_vacancy_;
__first_vacancy_ = __first_vacancy_->__next_vacancy_;
return result;
}
return nullptr;
}
void* __allocate_in_new_chunk(memory_resource* upstream, size_t block_size, size_t chunk_size) {
_LIBCPP_ASSERT_INTERNAL(chunk_size % block_size == 0, "");
static_assert(__default_alignment >= alignof(std::max_align_t), "");
static_assert(__default_alignment >= alignof(__chunk_footer), "");
static_assert(__default_alignment >= alignof(__vacancy_header), "");
const size_t footer_size = sizeof(__chunk_footer);
const size_t footer_align = alignof(__chunk_footer);
size_t aligned_capacity = roundup(chunk_size, footer_align) + footer_size;
void* result = upstream->allocate(aligned_capacity, __default_alignment);
__chunk_footer* h = (__chunk_footer*)((char*)result + aligned_capacity - footer_size);
h->__next_ = __first_chunk_;
h->__start_ = (char*)result;
h->__align_ = __default_alignment;
__first_chunk_ = h;
if (chunk_size > block_size) {
__vacancy_header* last_vh = this->__first_vacancy_;
for (size_t i = block_size; i != chunk_size; i += block_size) {
__vacancy_header* vh = (__vacancy_header*)((char*)result + i);
vh->__next_vacancy_ = last_vh;
last_vh = vh;
}
this->__first_vacancy_ = last_vh;
}
return result;
}
void __evacuate(void* p) {
__vacancy_header* vh = (__vacancy_header*)(p);
vh->__next_vacancy_ = __first_vacancy_;
__first_vacancy_ = vh;
}
size_t __previous_chunk_size_in_bytes() const { return __first_chunk_ ? __first_chunk_->__allocation_size() : 0; }
static const size_t __default_alignment = alignof(max_align_t);
};
size_t unsynchronized_pool_resource::__pool_block_size(int i) const { return size_t(1) << __log2_pool_block_size(i); }
int unsynchronized_pool_resource::__log2_pool_block_size(int i) const { return (i + __log2_smallest_block_size); }
int unsynchronized_pool_resource::__pool_index(size_t bytes, size_t align) const {
if (align > alignof(std::max_align_t) || bytes > (size_t(1) << __num_fixed_pools_))
return __num_fixed_pools_;
else {
int i = 0;
bytes = (bytes > align) ? bytes : align;
bytes -= 1;
bytes >>= __log2_smallest_block_size;
while (bytes != 0) {
bytes >>= 1;
i += 1;
}
return i;
}
}
unsynchronized_pool_resource::unsynchronized_pool_resource(const pool_options& opts, memory_resource* upstream)
: __res_(upstream), __fixed_pools_(nullptr) {
size_t largest_block_size;
if (opts.largest_required_pool_block == 0)
largest_block_size = __default_largest_block_size;
else if (opts.largest_required_pool_block < __smallest_block_size)
largest_block_size = __smallest_block_size;
else if (opts.largest_required_pool_block > __max_largest_block_size)
largest_block_size = __max_largest_block_size;
else
largest_block_size = opts.largest_required_pool_block;
if (opts.max_blocks_per_chunk == 0)
__options_max_blocks_per_chunk_ = __max_blocks_per_chunk;
else if (opts.max_blocks_per_chunk < __min_blocks_per_chunk)
__options_max_blocks_per_chunk_ = __min_blocks_per_chunk;
else if (opts.max_blocks_per_chunk > __max_blocks_per_chunk)
__options_max_blocks_per_chunk_ = __max_blocks_per_chunk;
else
__options_max_blocks_per_chunk_ = opts.max_blocks_per_chunk;
__num_fixed_pools_ = 1;
size_t capacity = __smallest_block_size;
while (capacity < largest_block_size) {
capacity <<= 1;
__num_fixed_pools_ += 1;
}
}
pool_options unsynchronized_pool_resource::options() const {
pool_options p;
p.max_blocks_per_chunk = __options_max_blocks_per_chunk_;
p.largest_required_pool_block = __pool_block_size(__num_fixed_pools_ - 1);
return p;
}
void unsynchronized_pool_resource::release() {
__adhoc_pool_.__release_ptr(__res_);
if (__fixed_pools_ != nullptr) {
const int n = __num_fixed_pools_;
for (int i = 0; i < n; ++i)
__fixed_pools_[i].__release_ptr(__res_);
__res_->deallocate(__fixed_pools_, __num_fixed_pools_ * sizeof(__fixed_pool), alignof(__fixed_pool));
__fixed_pools_ = nullptr;
}
}
void* unsynchronized_pool_resource::do_allocate(size_t bytes, size_t align) {
// A pointer to allocated storage (6.6.4.4.1) with a size of at least bytes.
// The size and alignment of the allocated memory shall meet the requirements for
// a class derived from memory_resource (23.12).
// If the pool selected for a block of size bytes is unable to satisfy the memory request
// from its own internal data structures, it will call upstream_resource()->allocate()
// to obtain more memory. If bytes is larger than that which the largest pool can handle,
// then memory will be allocated using upstream_resource()->allocate().
int i = __pool_index(bytes, align);
if (i == __num_fixed_pools_)
return __adhoc_pool_.__do_allocate(__res_, bytes, align);
else {
if (__fixed_pools_ == nullptr) {
__fixed_pools_ =
(__fixed_pool*)__res_->allocate(__num_fixed_pools_ * sizeof(__fixed_pool), alignof(__fixed_pool));
__fixed_pool* first = __fixed_pools_;
__fixed_pool* last = __fixed_pools_ + __num_fixed_pools_;
for (__fixed_pool* pool = first; pool != last; ++pool)
::new ((void*)pool) __fixed_pool;
}
void* result = __fixed_pools_[i].__try_allocate_from_vacancies();
if (result == nullptr) {
auto min = [](size_t a, size_t b) { return a < b ? a : b; };
auto max = [](size_t a, size_t b) { return a < b ? b : a; };
size_t prev_chunk_size_in_bytes = __fixed_pools_[i].__previous_chunk_size_in_bytes();
size_t prev_chunk_size_in_blocks = prev_chunk_size_in_bytes >> __log2_pool_block_size(i);
size_t chunk_size_in_blocks;
if (prev_chunk_size_in_blocks == 0) {
size_t min_blocks_per_chunk = max(__min_bytes_per_chunk >> __log2_pool_block_size(i), __min_blocks_per_chunk);
chunk_size_in_blocks = min_blocks_per_chunk;
} else {
static_assert(__max_bytes_per_chunk <= SIZE_MAX - (__max_bytes_per_chunk / 4), "unsigned overflow is possible");
chunk_size_in_blocks = prev_chunk_size_in_blocks + (prev_chunk_size_in_blocks / 4);
}
size_t max_blocks_per_chunk =
min((__max_bytes_per_chunk >> __log2_pool_block_size(i)),
min(__max_blocks_per_chunk, __options_max_blocks_per_chunk_));
if (chunk_size_in_blocks > max_blocks_per_chunk)
chunk_size_in_blocks = max_blocks_per_chunk;
size_t block_size = __pool_block_size(i);
size_t chunk_size_in_bytes = (chunk_size_in_blocks << __log2_pool_block_size(i));
result = __fixed_pools_[i].__allocate_in_new_chunk(__res_, block_size, chunk_size_in_bytes);
}
return result;
}
}
void unsynchronized_pool_resource::do_deallocate(void* p, size_t bytes, size_t align) {
// Returns the memory at p to the pool. It is unspecified if,
// or under what circumstances, this operation will result in
// a call to upstream_resource()->deallocate().
int i = __pool_index(bytes, align);
if (i == __num_fixed_pools_)
return __adhoc_pool_.__do_deallocate(__res_, p, bytes, align);
else {
_LIBCPP_ASSERT_NON_NULL(
__fixed_pools_ != nullptr, "deallocating a block that was not allocated with this allocator");
__fixed_pools_[i].__evacuate(p);
}
}
bool synchronized_pool_resource::do_is_equal(const memory_resource& other) const noexcept { return &other == this; }
// 23.12.6, mem.res.monotonic.buffer
static void* align_down(size_t align, size_t size, void*& ptr, size_t& space) {
if (size > space)
return nullptr;
char* p1 = static_cast<char*>(ptr);
char* new_ptr = reinterpret_cast<char*>(reinterpret_cast<uintptr_t>(p1 - size) & ~(align - 1));
if (new_ptr < (p1 - space))
return nullptr;
ptr = new_ptr;
space -= p1 - new_ptr;
return ptr;
}
void* monotonic_buffer_resource::__initial_descriptor::__try_allocate_from_chunk(size_t bytes, size_t align) {
if (!__cur_)
return nullptr;
void* new_ptr = static_cast<void*>(__cur_);
size_t new_capacity = (__cur_ - __start_);
void* aligned_ptr = align_down(align, bytes, new_ptr, new_capacity);
if (aligned_ptr != nullptr)
__cur_ = static_cast<char*>(new_ptr);
return aligned_ptr;
}
void* monotonic_buffer_resource::__chunk_footer::__try_allocate_from_chunk(size_t bytes, size_t align) {
void* new_ptr = static_cast<void*>(__cur_);
size_t new_capacity = (__cur_ - __start_);
void* aligned_ptr = align_down(align, bytes, new_ptr, new_capacity);
if (aligned_ptr != nullptr)
__cur_ = static_cast<char*>(new_ptr);
return aligned_ptr;
}
void* monotonic_buffer_resource::do_allocate(size_t bytes, size_t align) {
const size_t footer_size = sizeof(__chunk_footer);
const size_t footer_align = alignof(__chunk_footer);
auto previous_allocation_size = [&]() {
if (__chunks_ != nullptr)
return __chunks_->__allocation_size();
size_t newsize = (__initial_.__start_ != nullptr) ? (__initial_.__end_ - __initial_.__start_) : __initial_.__size_;
return roundup(newsize, footer_align) + footer_size;
};
if (void* result = __initial_.__try_allocate_from_chunk(bytes, align))
return result;
if (__chunks_ != nullptr) {
if (void* result = __chunks_->__try_allocate_from_chunk(bytes, align))
return result;
}
// Allocate a brand-new chunk.
if (align < footer_align)
align = footer_align;
size_t aligned_capacity = roundup(bytes, footer_align) + footer_size;
size_t previous_capacity = previous_allocation_size();
if (aligned_capacity <= previous_capacity) {
size_t newsize = 2 * (previous_capacity - footer_size);
aligned_capacity = roundup(newsize, footer_align) + footer_size;
}
char* start = (char*)__res_->allocate(aligned_capacity, align);
auto end = start + aligned_capacity - footer_size;
__chunk_footer* footer = (__chunk_footer*)(end);
footer->__next_ = __chunks_;
footer->__start_ = start;
footer->__cur_ = end;
footer->__align_ = align;
__chunks_ = footer;
return __chunks_->__try_allocate_from_chunk(bytes, align);
}
} // namespace pmr
_LIBCPP_END_NAMESPACE_STD
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