aligned_allocator.h
Go to the documentation of this file.
// Copyright 2020 Google LLC
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef HIGHWAY_HWY_ALIGNED_ALLOCATOR_H_
#define HIGHWAY_HWY_ALIGNED_ALLOCATOR_H_
// Memory allocator with support for alignment and offsets.
#include <stddef.h>
#include <memory>
#include "hwy/highway_export.h"
namespace hwy {
// Minimum alignment of allocated memory for use in HWY_ASSUME_ALIGNED, which
// requires a literal. This matches typical L1 cache line sizes, which prevents
// false sharing.
#define HWY_ALIGNMENT 64
// Pointers to functions equivalent to malloc/free with an opaque void* passed
// to them.
using AllocPtr = void* (*)(void* opaque, size_t bytes);
using FreePtr = void (*)(void* opaque, void* memory);
// Returns null or a pointer to at least `payload_size` (which can be zero)
// bytes of newly allocated memory, aligned to the larger of HWY_ALIGNMENT and
// the vector size. Calls `alloc` with the passed `opaque` pointer to obtain
// memory or malloc() if it is null.
HWY_DLLEXPORT void* AllocateAlignedBytes(size_t payload_size,
AllocPtr alloc_ptr, void* opaque_ptr);
// Frees all memory. No effect if `aligned_pointer` == nullptr, otherwise it
// must have been returned from a previous call to `AllocateAlignedBytes`.
// Calls `free_ptr` with the passed `opaque_ptr` pointer to free the memory; if
// `free_ptr` function is null, uses the default free().
HWY_DLLEXPORT void FreeAlignedBytes(const void* aligned_pointer,
FreePtr free_ptr, void* opaque_ptr);
// Class that deletes the aligned pointer passed to operator() calling the
// destructor before freeing the pointer. This is equivalent to the
// std::default_delete but for aligned objects. For a similar deleter equivalent
// to free() for aligned memory see AlignedFreer().
class AlignedDeleter {
public:
AlignedDeleter() : free_(nullptr), opaque_ptr_(nullptr) {}
AlignedDeleter(FreePtr free_ptr, void* opaque_ptr)
: free_(free_ptr), opaque_ptr_(opaque_ptr) {}
template <typename T>
void operator()(T* aligned_pointer) const {
return DeleteAlignedArray(aligned_pointer, free_, opaque_ptr_,
TypedArrayDeleter<T>);
}
private:
template <typename T>
static void TypedArrayDeleter(void* ptr, size_t size_in_bytes) {
size_t elems = size_in_bytes / sizeof(T);
for (size_t i = 0; i < elems; i++) {
// Explicitly call the destructor on each element.
(static_cast<T*>(ptr) + i)->~T();
}
}
// Function prototype that calls the destructor for each element in a typed
// array. TypeArrayDeleter<T> would match this prototype.
using ArrayDeleter = void (*)(void* t_ptr, size_t t_size);
HWY_DLLEXPORT static void DeleteAlignedArray(void* aligned_pointer,
FreePtr free_ptr,
void* opaque_ptr,
ArrayDeleter deleter);
FreePtr free_;
void* opaque_ptr_;
};
// Unique pointer to T with custom aligned deleter. This can be a single
// element U or an array of element if T is a U[]. The custom aligned deleter
// will call the destructor on U or each element of a U[] in the array case.
template <typename T>
using AlignedUniquePtr = std::unique_ptr<T, AlignedDeleter>;
// Aligned memory equivalent of make_unique<T> using the custom allocators
// alloc/free with the passed `opaque` pointer. This function calls the
// constructor with the passed Args... and calls the destructor of the object
// when the AlignedUniquePtr is destroyed.
template <typename T, typename... Args>
AlignedUniquePtr<T> MakeUniqueAlignedWithAlloc(AllocPtr alloc, FreePtr free,
void* opaque, Args&&... args) {
T* ptr = static_cast<T*>(AllocateAlignedBytes(sizeof(T), alloc, opaque));
return AlignedUniquePtr<T>(new (ptr) T(std::forward<Args>(args)...),
AlignedDeleter(free, opaque));
}
// Similar to MakeUniqueAlignedWithAlloc but using the default alloc/free
// functions.
template <typename T, typename... Args>
AlignedUniquePtr<T> MakeUniqueAligned(Args&&... args) {
T* ptr = static_cast<T*>(AllocateAlignedBytes(
sizeof(T), /*alloc_ptr=*/nullptr, /*opaque_ptr=*/nullptr));
return AlignedUniquePtr<T>(new (ptr) T(std::forward<Args>(args)...),
AlignedDeleter());
}
// Helpers for array allocators (avoids overflow)
namespace detail {
// Returns x such that 1u << x == n (if n is a power of two).
static inline constexpr size_t ShiftCount(size_t n) {
return (n <= 1) ? 0 : 1 + ShiftCount(n / 2);
}
template <typename T>
T* AllocateAlignedItems(size_t items, AllocPtr alloc_ptr, void* opaque_ptr) {
constexpr size_t size = sizeof(T);
constexpr bool is_pow2 = (size & (size - 1)) == 0;
constexpr size_t bits = ShiftCount(size);
static_assert(!is_pow2 || (1ull << bits) == size, "ShiftCount is incorrect");
const size_t bytes = is_pow2 ? items << bits : items * size;
const size_t check = is_pow2 ? bytes >> bits : bytes / size;
if (check != items) {
return nullptr; // overflowed
}
return static_cast<T*>(AllocateAlignedBytes(bytes, alloc_ptr, opaque_ptr));
}
} // namespace detail
// Aligned memory equivalent of make_unique<T[]> for array types using the
// custom allocators alloc/free. This function calls the constructor with the
// passed Args... on every created item. The destructor of each element will be
// called when the AlignedUniquePtr is destroyed.
template <typename T, typename... Args>
AlignedUniquePtr<T[]> MakeUniqueAlignedArrayWithAlloc(
size_t items, AllocPtr alloc, FreePtr free, void* opaque, Args&&... args) {
T* ptr = detail::AllocateAlignedItems<T>(items, alloc, opaque);
if (ptr != nullptr) {
for (size_t i = 0; i < items; i++) {
new (ptr + i) T(std::forward<Args>(args)...);
}
}
return AlignedUniquePtr<T[]>(ptr, AlignedDeleter(free, opaque));
}
template <typename T, typename... Args>
AlignedUniquePtr<T[]> MakeUniqueAlignedArray(size_t items, Args&&... args) {
return MakeUniqueAlignedArrayWithAlloc<T, Args...>(
items, nullptr, nullptr, nullptr, std::forward<Args>(args)...);
}
// Custom deleter for std::unique_ptr equivalent to using free() as a deleter
// but for aligned memory.
class AlignedFreer {
public:
// Pass address of this to ctor to skip deleting externally-owned memory.
static void DoNothing(void* /*opaque*/, void* /*aligned_pointer*/) {}
AlignedFreer() : free_(nullptr), opaque_ptr_(nullptr) {}
AlignedFreer(FreePtr free_ptr, void* opaque_ptr)
: free_(free_ptr), opaque_ptr_(opaque_ptr) {}
template <typename T>
void operator()(T* aligned_pointer) const {
// TODO(deymo): assert that we are using a POD type T.
FreeAlignedBytes(aligned_pointer, free_, opaque_ptr_);
}
private:
FreePtr free_;
void* opaque_ptr_;
};
// Unique pointer to single POD, or (if T is U[]) an array of POD. For non POD
// data use AlignedUniquePtr.
template <typename T>
using AlignedFreeUniquePtr = std::unique_ptr<T, AlignedFreer>;
// Allocate an aligned and uninitialized array of POD values as a unique_ptr.
// Upon destruction of the unique_ptr the aligned array will be freed.
template <typename T>
AlignedFreeUniquePtr<T[]> AllocateAligned(const size_t items, AllocPtr alloc,
FreePtr free, void* opaque) {
return AlignedFreeUniquePtr<T[]>(
detail::AllocateAlignedItems<T>(items, alloc, opaque),
AlignedFreer(free, opaque));
}
// Same as previous AllocateAligned(), using default allocate/free functions.
template <typename T>
AlignedFreeUniquePtr<T[]> AllocateAligned(const size_t items) {
return AllocateAligned<T>(items, nullptr, nullptr, nullptr);
}
} // namespace hwy
#endif // HIGHWAY_HWY_ALIGNED_ALLOCATOR_H_
hwy::AlignedDeleter
Definition aligned_allocator.h:57
hwy::AlignedDeleter::opaque_ptr_
void * opaque_ptr_
Definition aligned_allocator.h:89
hwy::AlignedDeleter::operator()
void operator()(T *aligned_pointer) const
Definition aligned_allocator.h:64
hwy::AlignedDeleter::AlignedDeleter
AlignedDeleter(FreePtr free_ptr, void *opaque_ptr)
Definition aligned_allocator.h:60
hwy::AlignedDeleter::AlignedDeleter
AlignedDeleter()
Definition aligned_allocator.h:59
hwy::AlignedDeleter::ArrayDeleter
void(*)(void *t_ptr, size_t t_size) ArrayDeleter
Definition aligned_allocator.h:81
hwy::AlignedDeleter::free_
FreePtr free_
Definition aligned_allocator.h:88
hwy::AlignedDeleter::DeleteAlignedArray
static HWY_DLLEXPORT void DeleteAlignedArray(void *aligned_pointer, FreePtr free_ptr, void *opaque_ptr, ArrayDeleter deleter)
hwy::AlignedDeleter::TypedArrayDeleter
static void TypedArrayDeleter(void *ptr, size_t size_in_bytes)
Definition aligned_allocator.h:71
hwy::AlignedFreer
Definition aligned_allocator.h:170
hwy::AlignedFreer::AlignedFreer
AlignedFreer()
Definition aligned_allocator.h:175
hwy::AlignedFreer::operator()
void operator()(T *aligned_pointer) const
Definition aligned_allocator.h:180
hwy::AlignedFreer::AlignedFreer
AlignedFreer(FreePtr free_ptr, void *opaque_ptr)
Definition aligned_allocator.h:176
hwy::AlignedFreer::opaque_ptr_
void * opaque_ptr_
Definition aligned_allocator.h:187
hwy::AlignedFreer::free_
FreePtr free_
Definition aligned_allocator.h:186
hwy::AlignedFreer::DoNothing
static void DoNothing(void *, void *)
Definition aligned_allocator.h:173
highway_export.h
HWY_DLLEXPORT
#define HWY_DLLEXPORT
Definition highway_export.h:13
hwy::detail::ShiftCount
static constexpr size_t ShiftCount(size_t n)
Definition aligned_allocator.h:124
hwy::detail::AllocateAlignedItems
T * AllocateAlignedItems(size_t items, AllocPtr alloc_ptr, void *opaque_ptr)
Definition aligned_allocator.h:129
hwy
Definition aligned_allocator.h:27
hwy::AlignedUniquePtr
std::unique_ptr< T, AlignedDeleter > AlignedUniquePtr
Definition aligned_allocator.h:96
hwy::AllocateAlignedBytes
HWY_DLLEXPORT void * AllocateAlignedBytes(size_t payload_size, AllocPtr alloc_ptr, void *opaque_ptr)
hwy::MakeUniqueAlignedArrayWithAlloc
AlignedUniquePtr< T[]> MakeUniqueAlignedArrayWithAlloc(size_t items, AllocPtr alloc, FreePtr free, void *opaque, Args &&... args)
Definition aligned_allocator.h:151
hwy::FreePtr
void(*)(void *opaque, void *memory) FreePtr
Definition aligned_allocator.h:37
hwy::MakeUniqueAlignedArray
AlignedUniquePtr< T[]> MakeUniqueAlignedArray(size_t items, Args &&... args)
Definition aligned_allocator.h:163
hwy::AllocPtr
void *(*)(void *opaque, size_t bytes) AllocPtr
Definition aligned_allocator.h:36
hwy::AllocateAligned
AlignedFreeUniquePtr< T[]> AllocateAligned(const size_t items, AllocPtr alloc, FreePtr free, void *opaque)
Definition aligned_allocator.h:198
hwy::FreeAlignedBytes
HWY_DLLEXPORT void FreeAlignedBytes(const void *aligned_pointer, FreePtr free_ptr, void *opaque_ptr)
hwy::MakeUniqueAlignedWithAlloc
AlignedUniquePtr< T > MakeUniqueAlignedWithAlloc(AllocPtr alloc, FreePtr free, void *opaque, Args &&... args)
Definition aligned_allocator.h:103
hwy::MakeUniqueAligned
AlignedUniquePtr< T > MakeUniqueAligned(Args &&... args)
Definition aligned_allocator.h:113
hwy::AlignedFreeUniquePtr
std::unique_ptr< T, AlignedFreer > AlignedFreeUniquePtr
Definition aligned_allocator.h:193