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// 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
//
//
// 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 <algorithm>
#include <array>
#include <cassert>
#include <cstring>
#include <initializer_list>
#include <memory>
#include <type_traits>
#include <utility>
#include "hwy/base.h"
#include "hwy/per_target.h"
#include <mozilla/Attributes.h>
namespace hwy {
// Minimum alignment of allocated memory for use in HWY_ASSUME_ALIGNED, which
// requires a literal. To prevent false sharing, this should be at least the
// L1 cache line size, usually 64 bytes. However, Intel's L2 prefetchers may
// access pairs of lines, and POWER8 also has 128.
#define HWY_ALIGNMENT 128
// 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 = nullptr,
void* opaque_ptr = nullptr);
// 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)));
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);
}
// A simple span containing data and size of data.
template <typename T>
class Span {
public:
Span() = default;
Span(T* data, size_t size) : size_(size), data_(data) {}
template <typename U>
MOZ_IMPLICIT Span(U u) : Span(u.data(), u.size()) {}
MOZ_IMPLICIT Span(std::initializer_list<const T> v) : Span(v.begin(), v.size()) {}
// Copies the contents of the initializer list to the span.
Span<T>& operator=(std::initializer_list<const T> v) {
HWY_DASSERT(size_ == v.size());
CopyBytes(v.begin(), data_, sizeof(T) * std::min(size_, v.size()));
return *this;
}
// Returns the size of the contained data.
size_t size() const { return size_; }
// Returns a pointer to the contained data.
T* data() { return data_; }
T* data() const { return data_; }
// Returns the element at index.
T& operator[](size_t index) const { return data_[index]; }
// Returns an iterator pointing to the first element of this span.
T* begin() { return data_; }
// Returns a const iterator pointing to the first element of this span.
constexpr const T* cbegin() const { return data_; }
// Returns an iterator pointing just beyond the last element at the
// end of this span.
T* end() { return data_ + size_; }
// Returns a const iterator pointing just beyond the last element at the
// end of this span.
constexpr const T* cend() const { return data_ + size_; }
private:
size_t size_ = 0;
T* data_ = nullptr;
};
// A multi dimensional array containing an aligned buffer.
//
// To maintain alignment, the innermost dimension will be padded to ensure all
// innermost arrays are aligned.
template <typename T, size_t axes>
class AlignedNDArray {
static_assert(std::is_trivial<T>::value,
"AlignedNDArray can only contain trivial types");
public:
AlignedNDArray(AlignedNDArray&& other) = default;
AlignedNDArray& operator=(AlignedNDArray&& other) = default;
// Constructs an array of the provided shape and fills it with zeros.
explicit AlignedNDArray(std::array<size_t, axes> shape) : shape_(shape) {
sizes_ = ComputeSizes(shape_);
memory_shape_ = shape_;
// Round the innermost dimension up to the number of bytes available for
// SIMD operations on this architecture to make sure that each innermost
// array is aligned from the first element.
memory_shape_[axes - 1] = RoundUpTo(memory_shape_[axes - 1], VectorBytes());
memory_sizes_ = ComputeSizes(memory_shape_);
buffer_ = hwy::AllocateAligned<T>(memory_size());
hwy::ZeroBytes(buffer_.get(), memory_size() * sizeof(T));
}
// Returns a span containing the innermost array at the provided indices.
Span<T> operator[](std::array<const size_t, axes - 1> indices) {
return Span<T>(buffer_.get() + Offset(indices), sizes_[indices.size()]);
}
// Returns a const span containing the innermost array at the provided
// indices.
Span<const T> operator[](std::array<const size_t, axes - 1> indices) const {
return Span<const T>(buffer_.get() + Offset(indices),
sizes_[indices.size()]);
}
// Returns the shape of the array, which might be smaller than the allocated
// buffer after padding the last axis to alignment.
const std::array<size_t, axes>& shape() const { return shape_; }
// Returns the shape of the allocated buffer, which might be larger than the
// used size of the array after padding to alignment.
const std::array<size_t, axes>& memory_shape() const { return memory_shape_; }
// Returns the size of the array, which might be smaller than the allocated
// buffer after padding the last axis to alignment.
size_t size() const { return sizes_[0]; }
// Returns the size of the allocated buffer, which might be larger than the
// used size of the array after padding to alignment.
size_t memory_size() const { return memory_sizes_[0]; }
// Returns a pointer to the allocated buffer.
T* data() { return buffer_.get(); }
// Returns a const pointer to the buffer.
const T* data() const { return buffer_.get(); }
// Truncates the array by updating its shape.
//
// The new shape must be equal to or less than the old shape in all axes.
//
// Doesn't modify underlying memory.
void truncate(const std::array<size_t, axes>& new_shape) {
#if HWY_IS_DEBUG_BUILD
for (size_t axis_index = 0; axis_index < axes; ++axis_index) {
HWY_ASSERT(new_shape[axis_index] <= shape_[axis_index]);
}
#endif
shape_ = new_shape;
sizes_ = ComputeSizes(shape_);
}
private:
std::array<size_t, axes> shape_;
std::array<size_t, axes> memory_shape_;
std::array<size_t, axes + 1> sizes_;
std::array<size_t, axes + 1> memory_sizes_;
hwy::AlignedFreeUniquePtr<T[]> buffer_;
// Computes offset in the buffer based on the provided indices.
size_t Offset(std::array<const size_t, axes - 1> indices) const {
size_t offset = 0;
size_t shape_index = 0;
for (const size_t axis_index : indices) {
offset += memory_sizes_[shape_index + 1] * axis_index;
shape_index++;
}
return offset;
}
// Computes the sizes of all sub arrays based on the sizes of each axis.
//
// Does this by multiplying the size of each axis with the previous one in
// reverse order, starting with the conceptual axis of size 1 containing the
// actual elements in the array.
static std::array<size_t, axes + 1> ComputeSizes(
std::array<size_t, axes> shape) {
std::array<size_t, axes + 1> sizes;
size_t axis = shape.size();
sizes[axis] = 1;
while (axis > 0) {
--axis;
sizes[axis] = sizes[axis + 1] * shape[axis];
}
return sizes;
}
};
} // namespace hwy
#endif // HIGHWAY_HWY_ALIGNED_ALLOCATOR_H_